Thank you all for your response, as you guys and girls clearly have far better knowledge about this then i do i have another question:
I currently have a HD 6870 was thinking of upgrading to a hd 7950 (if i don't build a machine from scratch) but would i see a dramatic difference as my processor is a Phenom II X4 955 and with my limited knowlege I dont think that processor is all that great (?) would it bottleneck so to speak?
List your specs.
Being only one generation removed GPU-wise is absolutely no reason to upgrade, if you're looking for "a good time" to do so.