I'm in the same boat. Have a 920 D0 which is stable at 3.6ghz but i havent been able to get any more out of it. Been looking at ivy but the socket only has a year left which really puts me off more then anything.
I have ordered a GTX 680 now and i'll decided if i need to upgrade the cpu once i've done some testing. I'll let you know how i get on but the card i've ordered isnt going to be in stock till the end of next week.
You wont. I've not run mine at anything other than stock, 3.8 and now 3.9. But with 1x680 you will be absolutely fine at 3.6 I'm sure of it.
In fact, I'm pretty happy with my i7 920. It will have lasted me for just shy of 4 years if I do my build project (which is just a switch of mobo/cpu/ram/cooler) as Christmas.
It has been a fantastic investment. And to be honest, if there isnt any game out that demands more then I may delay further.
I'm interested to see how demanding these new BF3 maps are going to be...the last pack at Christmas (the largest maps ever) may force the upgrade.