Need help on a price vs. performance question

Hey all,
Have a little conundrum. I had my eyes set on the 27" iMac i5 3.1ghz to take advantage of the upgraded Video Card and VRAM. I found an open box buy from Best Buy on the 27" iMac i5 2.7ghz for $1,400 out the door after taxes.

The price I would pay after my 5% discount on a refurbished 3.1ghz from Apple would be $1,695 roughly.

Is the $300 worth the upgrade? I will be using it for mostly photoshop and trying my hand at video editing with some gaming thrown in. I currently have a C2D 2.4ghz from Sept of 2007 and would like to keep the newest purchase 4-5 years.

 

Thank you, I thought it was worth it but I just wanted to make sure I wasn't throwing money at something I wouldn't notice the gains from. It seemed to me the benchmarks were close and might not be worth the extra money at this time