Hi, currently I have a Radeon HD 6870 card in my rig, along with a Phenom II X4 955 cpu. I was wondering what GPU/s would be a good fit for my build? The MoBo I'm currently using is a ASUS M4N68T-M v2. It's an older build, so I feel like I've come close to maxing it out. Thanks for any help on the matter!