mak5698, those are great questions...I will say I am a huge KEF fan & have had many sets of KEF's over the years. I absolutely love the R-11's and still have them in another 2 channel system I have in a smaller room. The treble of the 328Be's are more smooth compared to the R-11's & yes I think it's due to the beryllium tweeter. There were tracks that the R-11's could sound a slight bit harsh on the high end & I don't hear that at all with the Revels. The were a couple reasons I made the move to the 328Be's for my main system & replace the R11's...
1. My main listening room is very large (26'x17') & I wanted a larger, closer to full range speaker that could push plenty of air & fill my room effortlessly with deep bass & a big soundstage. The 328's dig a bit deeper & I am very happy with their bass capabilities for 2 channel music to the point I don't feel I need a sub.
2. I was intrigued by the new 328Be's right off the bat, their measurements, size & I've always liked the sound beryllium tweeters bring to the table.
As much as I really love my R11's, the 328Be's are a full step up in every department...ultra smooth in higher frequencies, super wide soundstage, clean midrange & superb bass response. But to be fair the 328's are quite a bit more expensive than the R11's. For the money I don't think neither the R11's or the 328Be's can be beat.