The best way to troubleshoot a grounding issue is to place the motherboard on top of a cardboard box and preferably with an anti-static bag ontop of the cardboard box and your motherboard on top of that.
From there plug in only the RAM, graphics card, and keyboard...also make sure it's close enough to the case that you can plug in the PC Speaker to listen for beeps.
Remove the graphics card, see if it beeps, if it does, then try reseating the graphics card and seeing if it boots. If it doesn't chances are the cards bad.
Same thing applies to the RAM, pull it out, if the system beeps, reseat it, if it doesn't boot, chances are it's the RAM.
Beyond swapping out CPU's theres no real way to test between it being the CPU or motherboard, but if it is indeed a grounding issue, the board will boot up outside the case.