^+1. A 790GX can play Guild Wars at 1440x900 with decent settings and get over 30FPS in most areas. An Intel G31 on lowest settings might get 21FPS. The newer Intel (G45) is better than that, but it doesn't match the AMD offerings.
Is there a reason the graphics must be onboard? Even a weak PSU can support a 4670, which is a very good card for the money, and doesn't need an auxilliary power connector.