Once I see a 3570k beat my 5.5ghz 2500k, I will be impressed. But considering the ivy chips don't overclock for squat because of garbage thermals (Your liquid cooling wont work) you are better off getting the i7. Sorry to be so blunt.
Well yes and no dude - it's not like anyone needs more than 4.5ghz for 24/7 on any chip for gaming. In fact an i5 at stock will do anyone proud so it's kind of a mute point in that regard.
An IB build has many other advantages that SB doesn't depending on what you want (power consumption, pcie 3 if you go for twin modern cards and memory controller most notably for me). These things make up for a slightly lower clock than SB for most people who won't use those extra 200 mhz anyway.
You have a good chip at 5.5 but what's your 24/7 clock?
Take a look at this review which amongst other things compares the 2500k and 3570k both at 5ghz.
http://www.bit-tech....0k-cpu-review/1
You can see that the IB chip is a noticably better performer clock for clock and with a power consumption nearly 15% less than the 2500k at that clock too. They only used an H100 and whilst temps were right on the limits 4.5-4.7ghz is definitely achievable for most people and is approximately equivalent to a 2500k performance at 4.8-5ghz plus the other advantages.
IB is a worthy successor to SB
IF you don't already own SB. Because SB is still truly awesome! But let's not get into IB bashing like we did with BD where it was deserved.
I definitely disagree with the i7 argument - unless you are doing something beyond general use and gaming which needs the extra threads and 10-30% performance then you are paying a heck of a lot more, like 50% more (i5=£170 i7=£250) for something you will never use AND you are compounding the heat issue by adding hyper threading.
I'll accept your challenge of trying to beat 5.5 ghz on a 3570k! I'll doubt I'll do it but I will try (I have a couple of tricks up my sleeve but still only using watercooling) I'm defo going to get above 5 stable within temps! We'll see...