@tobor007 Something you might want to keep in mind is that making an amplifier work hard for a living will result in harsher less involving sound. This is simply because the amp will make more distortion.
Tube amplifier power is expensive relative to solid state (which is why the industry went in that direction decades ago) but tubes still offer something that is almost impossible to do with transistors. Smoothness- greater detail and depth... but the problem you are up against is that in most rooms your speakers are near criminally inefficient. What I mean by that is you can count the number of amps that actually sound like music on one hand that also have the power you'll be needing to accurately portray musical peaks. Especially in the case of tube amplifiers, getting bandwidth at the same time as getting the power you need is almost impossible due to the constraints of the output transformer. The more power an output transformer can handle, the less bandwidth it has. Most tube amps of 200 watts struggle to do 20Hz to even 15KHz!
To avoid phase shift which affects the soundstage and tonality, you need that bandwidth (or else way more feedback than can be applied to a tube amplifier)! We make an output transformerless tube amp that makes over 500 watts, but its not practical for a speaker like this, I'm thinking mostly out of budget constraints as it costs about $147,000 for a set. But it makes the bandwidth no worries.
So if you are wanting the musical aspects that primarily are offered by tubes, you might want to think about getting a set of speakers that are easier to drive! There is absolutely no reason why a more efficient speaker would have any less resolution and you'll certainly experience greater dynamic punch as higher efficiency speakers have less thermal compression; I really can't think of a good reason to have a speaker with such low efficiency. So if you really want to get the most out of your amplifier dollar investment, you'll be doing yourself a huge favor to get something that's a bit easier to drive.
To illustrate how important this is, imagine instead of 85dB that the speaker is instead 95dB. The amplifier you would need to make the same undistorted sound pressure would be 1/10th the power! Instead of 500 watt you would only need 50, and there are many 50 watt tubes amps that would suit. The dollar investment goes down- you flush less dollars down the loo and get greater satisfaction out of the system.
