The upgrade path of LGA 1150 looks pretty poor anyway, I've just found an i5 3570k for £130, they are normally £160 and an i5 4670k is normally £170. Would you guys get the Ivy Bridge of Haswell? I head IB is better at overclocking...
The improved TIM will be the largest gain, higher overclocks.
OP, the 3570k would be fine. If it were up to me I'd look at the Z97 motherboards and i5 4670k or wait for the 4690k (it's expected to release around 2nd June, some have speculated as late as September).