What Power Amplifier Should I Buy?

The brands I think of are horrible choices: ZU Audio and Klipsch.

@kevemaher I don't see any problem with the ZUs. They easily keep up with the studio monitors @lynn_olson was recommending. The Klipsch, harder to say; if you want the most dynamics you get one of their horn systems but as far as I can tell they are (IMO) entry level to horns. I should qualify that by saying I've not heard a set in a controlled environment for quite some time. I would not be surprised to find out they are using computer optimization in their horns- anyone who doesn't do that these days is missing a bet!

I'm a fan of horns also; they have controlled directivity so can be used to minimize side wall reflections which otherwise contribute to harshness and of course they are much easier to drive!

You might consider a set of Deadalus loudspeakers which are typically about 95dB (meaning you'll need about 1/10th the power to get the same sound pressure in your room as opposed to the speakers you have now) and are reasonably priced. There are plenty of other choices.

In reality, speakers with efficiencies in the 87 to 90 dB/meter range typically experience power compression with amplifiers more powerful than 100 watts,

@lynn_olson To be clear, the amplifier power is only part of that, the other being the lower the efficiency of the speaker, the more thermal compression regardless of the power of the amp. The exceptions of course are ESL loudspeakers since they don't have a voice coil. 

@kevemaher Its a bit of a stretch to call your speakers '8 Ohms'! If you look at the impedance curve on the ASR site, you'll see that other than the box resonance, the impedance curve is closer to 4 Ohms (or less) in the bass region, where the power is most used.

There's a bit of math here; the woofer array of this speaker uses two 8 Ohm drivers wired in parallel for 4 Ohms. Since the sensitivity of the speaker is a Voltage measurement (2.83 Volts at one meter) the impedance of the speaker makes a difference.

So if 2.83Volts into 8 Ohms is 1 Watt, but that same Voltage into 4 Ohms is 2 Watts- a 3dB difference. If you were using the 8 Ohm taps on your Cary, it would have been struggling and no surprise you didn't get that 'tube sound'!

With tube amps the Efficiency spec (1 Watt/1 meter) is more useful since tube amps don't double power as the load impedance is halved. We already know the numbers, you simply subtract 3dB from the sensitivity value if a 4 Ohm load to arrive at the Efficiency, so only about 85dB.

If you want 'more dynamic' I really would consider getting a speaker that is both higher efficiency and also higher impedance (like actually 8 Ohms instead of '8 Ohm compatible' or '8 Ohms Nominal').

You don't lose any resolution by having a speaker that's easier to drive. In fact you may get more since hard to drive speakers cause power amplifiers to make more distortion, and distortion obscures detail. You want your amplifier to be loafing to do its job! That is when it will be the most musical.