If you are prepared to step out of the hifi industry, then there are plenty of active (and "powered") monitors available in the pro audio world - genelec etc..
The brand that most successfully stradles the pro/consumer base in the active market is ATC though - although quite how successful it is possible to be in that segment is questionable given ATC's rather small size :-)
That said, I have a setup like Lazarus28, ATC 50's as mains and active 10's as rears (phantom centre, I might buy a c4c :-) sometime..)
You *can* go wrong with ATC though if your in the US - the brand is virtually unknown and the products move slowly; for those reasons I picked up brand new 50s/10's for less than two thirds of retail!! The point I'm getting to is: either buy used, or bargain hard :-) Active 10's move really slowly on the used market and if you're lucky you should get a pair for $1500 - and for that they are an absolute steal.
The other downside with the 10's (and I expect the 20's) is that they run as hot as a skillet [perhaps it's just the pair that I own??] I turn mine off most of the time to save electric here in sunny california... Because of the heat, I wouldn't put them on a bookshelf without good ventilation - moreover, they seem to work best a few feet from the rear wall.
I've owned Meridian too, and thought them pretty good (although it was 15yrs ago - eek!). I've also done "linn style" active speakers (isobariks) with external amplifiers which is a great wiring puzzle and a lot of boxes and other crap which clutter up the living room. Don't waste your time with Linn/naim and active - it's a dead end (and an *insane* amount of money..)
Depending on how much bass you like (and generally how loud you like things) you might want to consider the new active 20's (not the older floorstanding model). They are like a bigger 10. That said, I never heard the 20's - I jumped straight from the 10's to the 50's and, apart from the back breaking wieght, I'm convinced they are the best speakers I've ever owned or heard. I think the 50's sounded better than B&W signature 800's and Wilson Watt/puppies - both being driven by huge levinson rigs.. [That said, those demo's convinced me to by a Levinson 390S CD player, which goes direct to the atc's..]
Also check out the CA2 preamp for the 10's - someone is selling one right now for $800 and that is bargain (if I didn't own an SCA2 I'd buy it myself :-))
Good luck,
Andrew
