Don't let the size of the speakers fool you. They need a relatively powerful amp. Make sure the amp or receiver you choose provides enough real watts to make the speakers perform their best. I would recommend any current model NAD, Marantz or H/K receiver for the KEFs.
A while back, I had KEF c-40s running off a NAD amp and did not like the results. There were undoubtably other factors involved, but I thought I'd bring it up.