I have a pair of 603 S3's in a room about 12 X 15. I use them in a 2-channel set-up as the main speakers. I tried driving them with several different tube amps and I did not like the sound. The cabinets seemed to be too active and resonate on the midrange. I read somewhere that they like alot of solid state power so I tried an Adcom 5500 - much better. Room placement is no longer as critical and sound is clean.