IMO if you buy a PC from one of those ~specialized Music Computer vendors, you're wasting your money.

any good spec'd Centrino or AMD64 (or P4.. but for laptops the other are preferable) running XP that you've run through the tweaks @ musicxp.net is more than 'music ready'. even before the musicxp stuff it's music ready. get as much RAM as you can afford and a fast drive. done.

in which case the answer to your question is HP.com, Toshiba.com, Dell.com, etc etc.. If i were to have a PC i'd probably buy another AMD64-based HP.