2011 iMac, Is it worth it.?

Don't be deceived by the question, i'm getting the 27" iMac. What I wanted to know is it worth it to get the $2,000 over the $1,700. The only difference is one has 2.7 GHz and the other has 3.1 GHz, also one has an AMD Radeon HD 6770M with 512MB and the other has a AMD Radeon HD 6970M with 1G. I just wanted to know if it was worth the extra $300, the computer is already a lot. I don't wan't to add to the price. I would appreciate is someone experienced in computer answered my question. Thank you.