Intel i7 vs intel t9300 processor

The Core i5 and i7 processors have Turbo Boost, which allows them to clock a little faster than your Core 2 Duo. All 3 processors also have Hyper Threading, which allows them to handle more tasks than your Core 2 Duo.

I think the i5 and i7 will have better performance in more recent games, but if your system is running fine right now, you shouldn't be worried.