Sup3rPsycho :
I have a duel-core 2.5 ghz cpu and the MSI HD 6450. If i get a stronger card does it also mean that i have to get a stronger CPU?
Technically speaking, no. Its the game you're playing that may (or not) demand a faster CPU, it doesn't actually have anything to do with the video card itself. The simplest way to look at it is that each game has its own workload for the GPU and CPU, and the one that struggles more with its workload will determine your actual performance. Some games really demand a fast processor, some demand so much from your video card that the processor barely even matters.
If you're upgrading from a really slow HD 6450, I think you will see some improvement even with a terrible CPU.