The difference between an i5 and i7 for gaming is going to be soooo nominal, you'd be muich better off going with a i5-750/760, and use the money saved to buy a better GPU.
The primary difference between a i5-750/760 and i-7s are HyperThreading and Dual Channel vs Triple Channel memory.
For those that don't know, HT is when the chip runs 4 more virtual threads, making it simulate a 8-core processor, which is pointless for gaming, and produces significantly more heat under load. Most games don't even utilizes 4 threads, much less 8. The difference between triple channel and dual channel is negligent as well, 4gb of memory is more than enough for gaming.. unless your encoding video, running paintshop, firefox, watching a blu-ray and etc simultaneously while playing FFXIV. Triple channel is the process of running memory in a series of 3, whether is be 3gb, 6gb, or 12gb.. you get slightly better performance, most of which won't apply to gaming.
I also happen to own both.. I have an i7-920 at 4.0, HD 5870 (875/1275), 6gb ram.. I've also recently built an i5-760 at 3.8, HD 5850 (890/1200), 4gb ram. Surprisingly.. the performance is very similar.. possibly only about a 5-10% difference at most for this game. As far as the benchmark scores, The i7-920 system scores ~5100, while the i5-760 system runs ~5000.
So in summary.. the difference between the two very nominal, and you're looking to save a couple hundred dollars, you would be much better off building a system around an i5-760.
Here's a link for a very good combo deal.. only $304 http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.492250 Edited, Sep 24th 2010 4:56am by zeruin