[wallot]

for gaming upgrade your video card E8500 is more than enough.

these days until nvidia fermi comes only new 5850/5870 radeos are really the choice for the future

for cheaper cards nvidia GTX275 is a good buy.

GTS250 is a low end than wont allow you to play at higher resolutions with high details.

450W PS is ok if it not a junk.
My PC takes 310W at full utilization when gaming and I got
E8400, 6GB RAM, 8800 Ultra and bunch of hard drives and lots of fans