[Solved] Bad Mobo, Memory or PSU? Boot with no video

System:
Asus A8R-MVP
AMD A64 3200+
G.Skill PC4000 2x2GB
Sapphire X1800XT
Corsair CX430 PSU (previously Antec NeHE 430W)

Reviving this PC after about 18 months in storage. Troubleshooting done so far:
- Cleaned the inside and tried to boot. No video and no post beep codes (ordered a PC speaker to be able to hear post codes since my mobo doesn't have an integrated speaker or LED indicators)
- Verified good monitor/video cables by booting with different PC
- Tested Antec PSU; PSU 5V rail failed test so...
- I ordered/installed the Corsair HX430 (passed PSU test before it was installed)
- Tried to boot with new PSU; still no boot with no video
- Breadboarded with only GPU, CPU, Memory; failed to boot with no video
- Removed GPU, received 1 prolonged, 3 short POST code
- Replaced GPU with a known good GPU, failed to boot with no video
- Reinstalled GPU and removed all RAM; I received NO POST code without RAM installed
- Reinstalled RAM, boot with no video.

With those indications, I am thinking I either have a bad mobo, memory, or PSU. I really don't think it's a bad PSU at this point. No POST beeps without RAM installed tells me that I probably have a bad mobo. Am I missing something? Any help in isolating the problem would be greatly appreciated - thanks in advance!

Looks like motherboard unless you forgot to hook up power to something like GPU.

Best answer selected by Rugger.