All the graphics parts that actually matter the most are all CPU dependent.

A lot of the GPU stuff can be turned off without making the game looks worse. I actually turn a lot of the GPU bound stuff off anyways like Depth of Field and AA.

So as long as your CPU is solid, you should be fine. The game can/will dip if you start building a sh*t ton of stuff in a single area though, but this happens even on the most powerful rigs.