I used to do the Max chopper thing and build my own, but have found recently the guys I get my parts from are selling the towers, w/o operating systems, for cheaper than I can put them together. Have sent several friends there and no one has had a complaint of any kind.
I should mention I am a big fan of AMD processors, which saves some coin right off the top
http://www.netdeals4u.com/category_s/264.htm they do ship also.

H.C.C.M.F. Local 6978
http://hondacb750parts.net