I'd suggest going with a big Valve Amp. I prefer single-ended, so 845 power valves are usually necessay to get the extra power to drive a bigger selection of speakers.
It is surprising what you can achieve with KT88's though, and a well designed Push-Pull Amp can sound pretty good too and give you the extra 'welly'!
I'd second some of the comments on here, to look at Unison Research Amps. Very reliable, beautifully designed and built to last a lifetime.
I found that some speakers can make valves sound a bit too rich and syrupy. Teamed with Focal speakers, which tend to be very neutral, valves are a great baance.
The great thing about valve Amps is that you can further tailor the sound depending on what make of preamp valves you use. Brimar and Mullard being warmer, Mazda having a bit more punch, Siemens and Telefunken being very open and neutral.
Good luck with your search!