About powering the amp with the pc power supply... it created a nasty ground loop, so I heard pretty much everything through the speakers, like that hard drive being accessed and crap.

I ended up cutting up an old set of pc speakers and using the 12v brick that came with them to power it, now I have crisp clean sound.
That's cool that you are using the power supply to power the sound amp are you going to get a 12v Marquee light?
I already have a regular florescent light installed, so no need for a 12v marquee light.