My favourites are ATC's, the SCM20A's (or passives with a good amp). The 50's are great, but the room has to be too. The 20's are a bit more versatile in that respect.
I actually use Philips 534MFB's (motional feedback - does anybody remember them?). They don't sound worlds apart from the sound of ATC, which is why I like them, but the midrange is a bit on the soft side. If I had to replace them I would choose the ATC SCM50A's, but I can't afford that... so I hope I don't have to replace them.
Cheers,
Glenn