I'm a bitter Brit. I sold a GTX295 for £200 and the rest of my system (4GB, 160GB HDD, OS incl, E8400@3Ghz, 680W Hiper PSU, Thermaltake Soprano case etc) went for £200 (with crappy 17" monitor, ancient 7950GT gfx card, keyboard and mouse)
I dont think there's a massive market for 2nd hand pc's. I did figure i'd have got more on e-bay (which i hate) selling separately.
Good luck with it tho.