Yep, i agree quadcore at least with 2gb ram. Also probably want to stick with Win XP (64-bit) rather than Vista in my opinion if PC - Vista can be a bit chunky on the CPU. Also a half decent soundcard, for something basic can't really go wrong with EMU or M-Audio.

I buy my PC stuff from:

www.novatech.co.uk
www.dabs.com

Also depends on budget and how comfortable you are with installing/configuring PC, soundcards and audio stuff. If you have the cash or are not too PC literate dedicated audio PCs are a way to go. You get a preconfigured, optimised audio PC with software/hardware installed and an image disk from which to easily re-install the whole system if it screws up. Available form places like:

http://www.sub.co.uk/

For convienence these systems can be worth the extra £££s for some peeps.