Well, the 5850 is the fastest by far, so if the money isn't an issue for the person gifting the laptop to you, go for that one.
However, if all you want to do is KOTOR and TSL, any of them will run both on highest settings as if they were a joke. You could go way lower than a 240 or 5730 and still play them on high settings, after all, the games are both more than half a decade old now.
Hit And Run Poster Extraordinaire
--Too Dumb to Quit--