Oh wow! A lot has happened in the last few days. This is going to be quite a long post.
First and foremost, I think the Elac b5s are wonderful speakers. Straight off I could hear they had the kind of sound I was looking for - they were even-handed without being overly smooth and they had detail that drew you into the mix and this has got better and better. I've been playing them for about 8 hours a day for 6 days, on low volumes when I'm out. Tonally they are quite similar to my old Celestions but there is more separation in the imaging, a fuller mid-range and deeper bass. I'm getting a wider sound stage and the tweeters are beginning to sparkle without sounding shrill.
In no way do I think they are boxy or small-sounding as some have commented. I can hear what people mean when they talk about good timing, I think they are fast and agile. They can also rock and sound punchy (on about 40% volume), something I was worried about not getting as they have quite a low sensitivity of 85db and the Marantz mcr603 is not known for having masses of power. I think this must be down to their very careful design.
One thing I've noticed is that with the Celestions I was using the SDB to get the sound I wanted but with the Elacs this is not necessary with all but the thinnest recordings. Fleetwood Mac's Rumours on CD sounded half-hearted with the Celestions but has come alive with the b5s. Pretty much all is sounding great (for my music tastes anyway): indie, acoustic rock, psychedelic rock, 60s stuff, even 30s and 40s jazz (I'm no headbanger! ). If you like a forward sound then these might not be for you - perhaps not for big hip-hop or dance fans.
Anyway, recently I noticed that a certain well-known retailer was selling their remaining Monitor Audio silver 1s for a massively discounted price and today curiosity got the better of me and I pulled the trigger on them (tracked down one of the very last available reasonably near to me). So, got them home, opened them up and was immediately impressed with their build quality and even packaging. Up on the stands after the Elac had just poured out their aural bliss on three of my current fave tracks and what do I hear? They sound like they're playing behind some pretty thick velvet curtains and that's being polite. OK, I know there's breaking-in to consider (even the hardcore variety of reverse polarising them and playing them face-to-face for 4 days, the Elacs sounded pretty decent right from the off) and I also know that these speakers might need more air behind them than I can give them (about 8 inches, but I have them well away from corners) but they're going to have to improve mightily to make me believe.
As for the Elacs, I'm with the camp that find them to be something special.
Oh, and that well-known retailer? They've got them for a silly low price!*ROFL*