Well, buying prebuilt computers never been a good idea in terms of customization.
Build your next PC yourself
Anyways, FFX runs almost always fullspeed with a 2.4ghz Core2, though 3ghz is better to avoid occsionnal speed drops in heave areas. FFX-2 requires slightly more (slow FMVs aside). I dunno for the other game though. As a GFX card, you'd need at least upper-midrange, but obviously, even lower-highrange would be better (just to be sure)