well first off i have a 2500k at 4.7ghz and a 7970 i am thinking of upgrading my cpu or getting another 7970?. btw all is cooled by Custom WC'ing. if i get a new cpu should i get a 2600k or a 3770k(don't like the heat issues)
you'd notice the second 7970 in xfire more then a new cpu. That i5 is pretty much the pinnacle of gaming CPUs... when overclocked.
In short, you probably will notice the improvement a 2nd 7970 brings, you won't notice a difference with an i7-3770k or i5-3570k. Your i5 is overclocked at 4.7, its doubtful you'll be able to overclock an i5-3570k or i7-3770k high enough to give you any improvement in performance... overclocked to 4.5-5.0ghz your i5 is about the fastest gaming cpu you can get short of $1000
what exactly are you struggling to do with a 2500k and 7970? i don't think there is any significant performance increase getting a 2600k only in certain applications, a 3770k will yield a good 20-25% increase in performance in some tasks probably close to what your 2500k is overclocked, wait and save up and see what the new round of cpu's and gpu's bring thats what i reckon