|"I can tell you that your 400w PSU is way underpowered for one thing"|
Actually, the PC Power & Cooling MK III 400W is a quality unit that gets excellent reviews & has decent specs. I doubt it's the problem.
"I fear I may have blown one of my components"
Did you bench test your components before you installed them in the case? If not, that's where you went wrong. Now you have no idea if you have a hardware problem or something was installed incorrectly or is shorting out in the case. You can try testing within the case, here's what you need to do:
- remove the video card & connect the monitor to the board's onboard port
- remove all RAM except for one stick
- disconnect the HDD & DVD drive, both the power & data cables
- unplug all external devices except for the keyboard
- make sure the case wiring is connected properly to the board
- make sure the heatsink is installed properly, it's plugged into the proper fan header, & if you used thermal paste (rather than a thermal pad), make sure you applied it correctly. Proper paste application is critical. The i3 uses the 'vertical line' method:
After you've done all the above, power on the system & see if you can access the BIOS. If you can, tweak all the settings for best performance, save, & shutdown. If it doesn't boot, remove everything from the case & try a 'real' bench test: