Speaking solely to i5 versus i7, I just yesterday assembled all of the components for a build in this same price range, and I went with an i5. I did spend some time comparing the i7 to the i5, and my final thought was that for gaming purposes mixed with some browsing and other simple tasks, the benefit of the i7 would be so small as to not justify the added cost.
Now, I plan on going with crossfire as well, and yes, there is that 8x limit with the i5, but I still didn't feel like grabbing the i7 was quite justified for its cost. Will I lose something? Of course. But is it worth the extra $80-$100 or so to fix? I didn't think so.
Now, this was just my own analysis and experience, so I can't say what would be best for you. And I can't speak beyond the i5/i7 comparison. I felt like the i5 was a great choice, all things considered.
I did a little more digging on this topic and found this article: http://www.tomshardware.com/reviews/core-i5-gaming,2403.html. The comparison isn't using quite the graphics card you want, so it's not perfect, but it at least gives you an idea of the kind of differences you're looking at for the i5 versus the i7.
Yeah ok he would get better performance from a 58xx card, but he has a budget of $1000
An AMD setup with a 955 or similiar isnt that much cheaper than a ci5 750 setup
With the parts i listed he's already over budget and theres no OS
Actually I did not see he needed a monitor in that mix as well. Not sure I can get it under 1K with a monitor and a 58XX.
However if he gets a 5770 then he will be bottle necked by his GPU p;laying at 19XX resolution. If it is strictly for gaming he might want to bump the processor down even more since games are almost strictly driven by the GPU.
1K does not leave much room to play with when you need to throw in a Monitor and a OS.
Looks like if he could stretch the budget by about 60 bucks he could get a 5850 but that is as close I can get with a 955. So I still stick with my thought of bumping down the processor some more to fit in the 5850.