Local tech support that can test hardware?

I'm having a real gordian knot of a problem with my PC that as far as I can tell has to be a hardware issue at this point, and it's hard to find shops with the stock on hand to be able to swap out hardware and find the problem. I already took it to a smaller shop who wasn't able to do as much, but was able to rule out any software or RAM problem. Any pointers or recommendations?