All I use my computer for is to play CM, internet DSL, downloading and playing tunes off the internet and some word processing. That's all I need.
you shouldnt need anything more advanced than a 1Gz processer, 256mb SDRAM and a poxy ol geforce2 GTS
CMBB wont tax your computer much (correct me if im wrong)
its not like your playing current first person shooters, or the like.
dunno what that would cost in the states, but here in New Zealand it would be very cheap for a computer at those specs, in fact they dont even really advertise computers that low spec these days