Cooling and noise is a big part. I like investing in a silent PSU, swap the case fans for silent ones and get a good heatsink/fan for the particular gpu and cpu (they make specific ones for each model) usually by zalman or arctic cooling. You could go down the road of watercooling too, since its evermore accessible these days.
Case wise, I' d go for either Coolermaster or Antec as emo said. Big, spacious, thermodynamic, well thought out designs that look sleek. Expensive for a case but if you' ve no budget its worth it.
The motherboard will depend on the speed of RAM, FSB for the CPU, whether you want SATAII, SLI for the gfx card, ethernet speeds, overclockability and other features. In the end its just picking one that suits your needs.
And then I guess sounds the other big area, but I suppose an x-fi and a decent surround system will do you as you said you' re not a big audiophile. Some PC games are all about the sound.
I cant believe your making another PC though, you crazy person.