With a Z97 you can have 'any' Haswell CPU. Would strongly recommend a second hand CPU (same performance for less money or more performance for the same money).
i5 in this case (CeX or eBay are your bestest friends).
EDIT:
i5 from CeX: i5 4430 for £110 i5 4440 for £125 or i5 4460 for £130.
i5 from eBay: i5 4460 for £100 (BiN) or various i5 CPUs in auction between £80 and £120.