I own the RS6's, and have heard the Energy's (in a dealer's sound room)... IMO, the RS6's are a relative bargain; terrific sound quality, detailed, terrific build quality. Some people find them bright; a friend of mine dislikes Monitor Audio, & says he finds the bass of the RS6 especially to be a bit on the boomy side (that is NOT my opinion). I've always respected Energy speakers, though I've never owned a pair...it just seems I always find something else I prefer when I buy speakers.
You'll just have to audition the RS6's to decide for yourself. Again, I think they are great, and to me, are a bargain as a sub-$2,000 speaker... My 2 cents...