NAS Built With Consumer Grade Components Won't Boot

I have recently switched out the power supply and boot drive of a NAS I built. I also added a DVD drive and two screws to the motherboard (which have since been removed). After I did this, pressing the power button has no effect.

Parts list: http://pcpartpicker.com/user/john01dav/saved/#view=b96kcf (I replaced the PSU with a CX500, and the DVD and boot drive with the cheapest on at a store near my house -- I can't get the exact model because the computer won't boot)

As per the advice of the Ask Ubuntu chat, I tried the following things (in this order):

1. Ensure that the power supply's switch (and voltage switch (only the old PSU has a voltage switch) are in the proper location
2. Remove nonessential components (discoect SATA and power from hard drives and DVD drive, there is no video card except that which is built-into the motherboard)
3. Tighten front panel coectors
4. Use the old PSU without remounting it in the case (sitting on my desk)
5. Try another case's power button
6. Try using a screwdriver to boot the computer (this worked once with the old PSU after tightening the 24-pin coector (I couldn't see the screen because I am testing for boot without one, but all fans and appropriate LEDs came on), but, after recoecting the new one it failed and failed again after recoecting the old one)

I have not yet tried starting the PSU by jumping it's 24-pin coector as I do not have a wire (or paperclip) with which to do this. I would like, if possible, answers that assume that this was tried and failed as all it does is test for a bad PSU and I don't belive that either PSU is dead because one worked with item number 5 in the list above and the new PSU was apparently tested by the store I bought it from.