I've had the pleasure of auditioning some pretty fancy amps including some tube amps which cost more than a nice car. Let me start by saying that I've heard some beautiful music reproduced by solid state amps, but certain tube amps sound better - my opinion, there are folks on this board who laugh at the idea. Anyway, I have no idea about how these things work, turn them on, wait a minute while the glass bottles start to glow and then music comes out the speakers. As to solid state, I have even less of an idea - so take what I say with much salt.
From my experience, SET amps and amps which use 300B type tubes sound the best. Price is not the determinative factor. I've heard sub $1000 amps which sound better than >$10,000 monoblocks. You may want to schlepp your speakers down to a snotty high end audio shop (probably better to ask first) and audition their tube stuff.
You may want to talk to the folks at Divertech
http://www.divertech.com/antiquesl.html distributors of ASL magical amps in NA and ask them which amp is like the MG S1 15DT but puts out more power in SET mode.
You may consider contacting Kevin at Upscale Audio, knowledgeable and pleasant, he sells ASL and other stuff as well - loves music and loves his tube toys. He can give you some good advice.
http://www.upscaleaudio.com/
