If you're looking for a good midtower, I highly recommend the Antec 300 Midtower, retail: $39.99 - $49.99
Durable steel construction, Optional 2x 120mm intake fans, factory 140mm top exhaust fan with speed control, 120mm exhaust, removable filter in bezel. PSU located on floor. The only minuses are no removable MB or HD trays, but it's hard to find everything at this price range.
My video review of Antec Three Hundred
Antec 300 Three Hundred Review
Heres an Antec 300 I modified for a customer. A 92mm hole in the floor beneath the PSU provides plenty of ventilation.
I also added u-channel
to the hole for a professional finish. If you wish your PSU traditional way, not upside down.
I also install side panel windows in Antec 300s.