The best center to get would indeed be the KEF one that matches your mains. Another good option might be the BIC DV62CLR. A highly rated center channel, at many price classes higher than its own.
As for speaker cable, just some good 12awg wire (stranded for easy management) will work fine. My favorite is the Belden 5000UE wire from
Westlake Electronic. Great prices, and good in-wall rated wire, so it can be your total solution.
Bare wire is always an option, but you can find some cheap banana plugs around that will dress up and simplify your terminations.