I run a Yamaha receiver and a CA 640 V1 CDP with the MA RS6 's . I use them with off air TV, movies and stereo music, and must say that I'm very happy with this configuration. Although the yammie isn't up to speed in the bass department (not very controlled, tight bass), the overall experience is very good. I'm thinking about switching it for a CA of Arcam stereo amp in the future.
From what I know about the kefs, they are very good, but not worth the extra money to the MA's. In fact, they're worse! They are quite large too, compared to the MA's. Last of all, I prefer the looks of the MA's to those of the Kefs. real wood vineer simply does it all!
Very well recommended! good luck!