Why the Lian Li B4-mATX Is the Best Small Form Factor Case for Most Builders
Small form factor cases are compact enclosures designed to fit Mini-ITX or microATX hardware while still supporting modern GPUs, adequate cooling, and an appropriately sized PSU, enabling high-performance systems even in tight space PC building scenarios. For most people, the Lian Li B4-mATX is the best starting point because it proves you can get a capable, affordable chassis without sacrificing component support or airflow. Its 420 x 191 x 288 mm footprint keeps it firmly in the small form factor cases category, restricted to Mini-ITX and mATX motherboards. Yet it still allows some of the largest RTX 5080 graphics cards to fit, so you can plan high-end mini-ITX builds without worrying about GPU clearance. At USD 69.99 (approx. ₱3,900), the B4-mATX delivers strong mATX case cooling via two pre-installed 120 mm top fans and room for additional fans on the front, bottom, and sides.
According to the manufacturer’s specifications, "The Lian Li B4-mATX measures a mere 420 x 191 x 288mm so only Mini-ITX and M-ATX motherboards need apply" and still supports oversized GPUs. To keep thermals in check when adding a 360 mm AIO, you must use an SFX compact PC case PSU, which frees up space and avoids radiator/PSU collisions in this tight layout. This is a clear illustration of how matching PSU form factor to case constraints prevents thermal and cable management headaches. The optional AeroDeck support lets you orient the system traditionally or vertically, useful if you want to optimize airflow paths for your specific mini-ITX builds in confined desks or media cabinets. Overall, the B4-mATX hits the sweet spot of size, price, and power potential.
ASUS Prime AP304: Curved Glass and ATX 3.1 Power for Future-Proof Compact Builds
If you want a compact mid-tower that looks premium and is ready for next-generation power standards, the ASUS Prime AP304 is the confident pick. Its defining feature is a seamless curved tempered glass panel that runs from front to side, turning the case into a panoramic window onto your components while keeping a compact footprint relative to traditional mid-towers. Cooling is handled through a patented slot vent design that pulls air from intake vents slightly above the bottom, directing it straight toward heat-heavy components like the graphics card. The ARGB variant comes pre-equipped with four 28 mm thick MR120 ARGB fans, one at the rear and three on the side, designed to balance static pressure and quiet operation at a maximum of 21 dB(A). This makes the AP304 an excellent choice if mATX case cooling levels are desired in a visually striking ATX chassis.
Expansion support ensures you are not boxed in as GPUs and coolers grow more demanding. The Prime AP304 handles graphics cards up to 420 mm, radiators up to 360 mm, PSUs up to 200 mm, and CPU air coolers up to 175 mm, which comfortably covers most high-end tight space PC building plans. Pricing for the ARGB model is ¥26,480 (approx. USD 164 / ₱9,200), while the non-ARGB version comes in at ¥21,980 (approx. USD 136 / ₱7,600). ASUS pairs the case with the TUF Gaming Gold EVO PSU series, which delivers 80 PLUS GOLD efficiency, is fully modular, and compliant with ATX 3.1, including native PCIe 5.1 and a 16-pin PCIe cable for upcoming GPUs. Choosing an ATX 3.1 PSU here is the right move: power delivery is stable, cabling is clean, and you are ready for next-gen 12VHPWR-style connectors without adapters cluttering your compact PC case PSU routing.
SAMA S50: Unconventional PSU Placement for Better Airflow in a Compact Mid-Tower
The SAMA S50 is a compelling alternative if you want a compact mid-tower that solves airflow and cable management in a different way. This case supports ATX, microATX, and ITX motherboards, but it stands out because the power supply is not mounted at the usual bottom location; instead, it is installed on the side behind the front panel. This unconventional layout opens the bottom of the chassis for extensive ventilation, with room for up to three 120 mm fans and a full-length magnetic dust filter grille. The side panel opposite the glass also carries a large vent backed by a magnetic dust filter, improving intake and exhaust options. Together with four pre-installed 120 mm ARGB fans and an ARGB/PWM control board, the S50 is built to keep air moving even in busy tight space PC building setups where multiple drives and cables might otherwise choke airflow.
With dimensions of 235 mm (W) x 426 mm (H) x 475 mm (D), a 410 mm GPU length limit, and 165 mm CPU cooler height, the S50 provides headroom comparable to larger mid-towers while still feeling compact on or under a desk. Its PSU bay supports units up to 180 mm long, and an interior jack routes mains power to the side-mounted supply, so respecting that 180 mm limit is essential to avoid clearance conflicts and messy cabling. Price is set at €99.90 (approx. USD 110 / ₱6,200). In practice, this innovative PSU layout proves that matching PSU form factor and length to the case’s unique geometry can deliver more bottom-to-top airflow and cleaner cable paths, which is valuable in higher-wattage mini-ITX builds housed in a larger chassis that still has compact aspirations.
Picking the Right PSU and Case Combo for Mini-ITX and mATX Builds
Across these three cases, the biggest wins come from aligning PSU choice with chassis constraints. In small form factor cases like the Lian Li B4-mATX, adding a 360 mm AIO means you must switch to an SFX compact PC case PSU so the radiator and cabling can coexist without obstructing airflow or component access. In the ASUS Prime AP304, choosing an ATX 3.1-compliant, fully modular unit such as the TUF Gaming Gold EVO ensures you have the correct 16-pin PCIe cable for next-generation GPUs, avoiding adapter clutter that can block the efficient slot vent intake path. In the SAMA S50, respecting the 180 mm maximum PSU length keeps the side-mounted supply from colliding with internal structures, preserving the integrity of its airflow-centric design. For mini-ITX builds and mATX case cooling goals, these examples show that power delivery, cable types, and physical PSU dimensions are as important as wattage numbers on the box.
- Buy the Lian Li B4-mATX if you want the best balance of price, small footprint, and modern GPU support for Mini-ITX or mATX builds.
- Skip the Lian Li B4-mATX if you need native support for large ATX motherboards or dislike using an SFX PSU for high-end liquid cooling.
- Buy the ASUS Prime AP304 if you value curved tempered glass aesthetics, quiet high-airflow ARGB fans, and ATX 3.1 PSU readiness for future GPUs.
- Skip the ASUS Prime AP304 if you are on a tight budget and do not need an ATX mid-tower with panoramic glass and extensive radiator support.
- Buy the SAMA S50 if you like its side-mounted PSU concept, strong fan and dust filter coverage, and gaming-focused ARGB presentation in a compact mid-tower.
- Skip the SAMA S50 if you prefer conventional bottom-mounted PSUs or if you need more than 180 mm of PSU length for existing power supplies.
