Basically, the 9800GTX+ and the HD 4850 both have advantages over each other. Some games go to the 4850, and some games go to the 9800GTX+. It is true that the 4850 does run somewhat hot, but it doesn't really matter since most video cards can handle 80c just fine. Either way, you would've made the right choice of buying the 9800GTX+ because it will give you a huge boost from your 8500GT.