I hate to ask, but why would anyone run a 2700K at stock speed? I've obtained seven 2700Ks so far, every single one of them runs at 5GHz just fine. Built another one yesterday. Doesn't need any fancy cooling at all (unlike the 4790K), I'm just using a simple old TRUE with one NDS fan (the TRUE was only 17 UKP off eBay).
To answer your question though, at stock speed (remember both those CPUs have their relevant Turbo levels aswell, the 2700K ramps up to 3.9, while the 4790K reaches 4.4GHz), the speedup if any would depend on the game, resolution, detail level, etc. I'm not familiar with TW3, has it been used in any reviews you can find of these CPUs? Or perhaps find a review of the game which tested hw requirements?
Overall though I doubt the speedup would be that much, the 2700K is still a potent chip (hence why I keep buying them because they oc so easily). If you want better fps with a CPU of this class, get a better GPU setup, though you're starting from a pretty good card already. Might need 970 SLI or something to be usefully quicker (check reviews for 780 vs. 980, not sure offhand).
Ian.
PS.
My site has lots of 2700K results, tested with 980s and others (no 700 cards yet, but you can extrapolate easily enough, eg. from 580 comparisons & suchlike). PM me if you'd like some 3DMark numbers. You can use the data to cross-check with reviews, etc.
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