I am planning on getting the AMD Phenom II x6 1090t and the ATI Radeon 6850, I wanted to know if it would bottle neck since the Phenom is pretty high class while the 6850 is only a premium GPU.
Well a bottle neck is when a particular component holds back another because of it's inability to deliver the required speed or performance the other component needs to perform optimally. In your case your gpu might be the slower out of the two, but it isn't capable of bottle necking the processor.