Stability and reliability. Nothing is more frustrating than troubleshooting an unreliable and unstable power supply. The best way to avoid this issue is by using a well know, trusted name in the power supply business...Seasonic.
Please make 500w sff and sff 700w! also with colored fans, blue or perferably red fan.
and must haves,
80 plus
quite
runs cool 30c/35c
modular
4x 6pin adapter
adapter plugs same color as fan
tight sleeving