do you have another machine to try the two Quadro 2s in? that's the first suggestion that comes to mind, because simply put, if the streaking appears in the BIOS setup screen, there's no chance whatsoever it's a software problem.
as far as I can remember, Quadro 2s do not have any sort of special power requirements (pretty sure the Molex connector started with the FX 5800/Quadro FX 2000). also, I don't think it uses the "Pro" aspect of the AGP slot, just the vanilla AGP. last ditch effort would be to open the machine up, reset the CMOS, and see if that does anything. but, there's definitely a fundamental problem if it happens before you reach any OS.
like I said before, it doesn't sound like a PSU issue. sometimes, though, motherboards just go bad for no reason that anyone can identify. they just go *poof* of their own volition.