I would like to keep the machine under $1500 including the case and Win7 OS. That seems pretty generous IMO.
I'm not quite sure what to do about the case. I don't want a monster-sized tower. I was thinking a mid-sized lian li case or possibly rackmounting it with the rest of my audio processing gear, but I have heard people discouraging this due to noise being introduced into the audio signals. I guess I could rackmount it in a separate rack.
Also, I would like to have firewire and maybe usb 3.0