i plan to play bf3 and skyrim at 1080p ultra settings
i could either get
3570k with hd 7870
3450 with gtx 670
Would you be willing to stretch your budget a little bit and go for a 3570k and a 7950?
The price difference between the 7870 and the 7950 is quite small...
You will max both games in any case, but the 3570k with it's overclocking potential will make future upgrades easier.