I've heard Revels, not the F12 mind you, but others in their line..."muffled highs and voices" is certainly not an accurate description of their sound IMHO. It sounds like the standard salesman-speak where they put down any speakers that they don't carry.
My reticence about Revel, when I heard them, was that they were a bit forward-sounding for me, with a hard/metalic-sounding top end. If the salesman's comments about the speakers were something like that, I might consider his opinion...in this case, based on what he said, I'd ignore him, and discount any advice he may have given.
It should be fairly easy in even any moderately-sized city to at least listen to other speakers within the same line of any PSB, Paradigm or Revel (or Focal for that matter) that you're considering - this is a lot of $$$ you're spending, you should really try to at least listen to the speaker lines with the same CD to get an idea of their characters.
If I had to simplify the differences between these lines' house sounds, Paradigm and Revel are more forward sounding with good weight in the bass. B&W are more relaxed with a focus on midrange, and PSB's are kind of in between the 2, with a more relaxed sound but better deep bass than the B&W's.