If your motherboard's processor socket is 775, then I suggest you buy atleast an Intel Core 2 Duo or Quad if you have more money. If you have a good GPU but a bad CPU then your graphics will be bottleneck'd. You should also upgrade your PSU to atleast a 650watts, 80 plus certified.
agree with everything you suggest - except 650w PSU
, absolutely no need
for the xtra cost that would entail. A 7750 requires only a 350w unit and that's
with headroom, if he wants to go with a 7770 then it's 430w with headroom.