Okay, let me correct you.
RAM doesn't cause overheating. I seriously doubt Minecraft would need more than 2GB, let alone 4GB.
A GT 310M would run Minecraft and WC3 just fine.
Lastly, why are you buying a laptop? A desktop would be much better for continuous use.
But if you really need the portability, you might want to build your own laptop @ XoticPC..
I am buying a laptop simply because of the fact that i want to carry it to school, hence the relatively small screen size.
I have checked out Xoticpc before, but the problem with this site is, that its from the US, and i simply don't buy anything from there, as i have had loads of bad experiences with wares from the US. And i already have a Desktop, which is fairly high-end (Not the one in my specs, I'm too lazy to refresh it )