What's your budget? The Cornwalls are pretty tube-friendly.
You don't need a lot of power so this is all about nuance. Smaller tube amps often have more bandwidth (although because our amps are output transformerless this doesn't apply to our amps) which allows them to be more spacious.
If you decide to go with an SET (Single Ended Triode) amplifier, keep in mind that whatever power the amp is rated, you will not want to exceed about 20% of that power in order to get the most out of that amp. With push-pull amps this isn't true- they typically have a much wider 'usable power' range (SETs are typically 10% distortion at full power; to keep that down and hear what they are really about you need to stick to that 20% rule). A push-pull amp that will do the job on a speaker with this sort of efficiency need only make about 15-30 watts. A lot depends on room size and how lively it is! Because of the lower power requirements, a triode amplifier is nice (and there are triode amps that are push-pull).
If you get this right you'll be hearing things in the music you didn't know were there and overall the system will also play in a more relaxed effortless manner. One thing to keep in mind- its not so much about money as it is about nuance. There are good inexpensive amps and there are good expensive amps, along with their opposites.
Are you planning monoblocks or a stereo amp? Balanced or single-ended connections? How big is your room and how lively is it? These are things that will help people here be able to help you more.
