Sporadic PSU Booting Issues

[BigDamn]

Hey there fellas. I've got a server that runs here at home that I use for network backups and whatnot. Its a pretty basic build, it has 2 7200 Seagate drives, an Athlon 2 X4 640 (OC'd to 3.7ghz), onboard graphics, and 8gb of DDR3. I've got a 450 watt Thermaltake PSU that came with an old case a few years ago, that would work fine, but for some reason it just can't power the 2 drives at once. Running a single drive it does fine. I've also got a Corsair CX500W that can power everything just fine, and once booted is flawless. However, whenever I do a full power down and try to boot back up it becomes a nightmare.

 

Everything in the PC powers on, fans, lights, HDD's, etc. but there will be no video and the motherboard doesn't beep. The other day I just ripped the power cord out of the back, plugged it back in, and it booted and ran for several days. Once again today I'm having the same issue, and that "solution" doesn't work. The Thermaltake PSU will boot just fine (with one HDD) but the Corsair will not. Currently I have the Corsair powering just the hard drives while the Thermaltake handles the CPU and motherboard and its running without issue. Anyone knows whats going on here? Thanks!