Well, I guess it's pretty cheap if you factor in the Mail in Rebate, but I never depend on getting those since half the time you don't ^_^. They are such a pain now. Anyway, it will be a big jump over that IGP. It really would be worth it to spend a little more on a GDDR5 version. Anyway, it should be o.k for the first Modern Warfare and Mass Effect, but that depends on the resolution. For Crysis though you're stuck to medium at 1024x768. Any higher than that and you have to start putting things on low with that card.
The card is obviously more effective when you overclock it. If it will be enough for you even then is something you have to decide. Just Google some reviews on the GT 240 and you'll see some on the GDDR3 versions