I concur with why0why,
There is a huge difference in performance in Class D amps based on how much they cost. Inexpensive amps use switching power supplies and limited feedback engineering and most of the time an off the shelf Ice power module. I have listened to several of these type of amps; they all have a huge amount of output power, especially in the lower end (which is why they are pretty much exclusively used now in sub woofers and that is where there is extremely low distortion. If you move on to a main power amp which of course is reproducing a very wide frequency range, the upper end is where things can get dicey. I have found the lower price range Class D amps tend to get a little harsh on the upper end to my ears and I a don't particularly enjoy it after a long period of listening.
Now fast forward to a very well engineered design in Class D such as the Anthem M1 monoblocks. These amps do not use any off the shelf power modules, it's all proprietary output design with an amazing liquid cooled output stage using alcohol filled copper heat pipes. The amps when fed with 240 volt main input loaf along with 2000 watts per channel and are stable down to 2 ohm loads where the output goes up much higher. If you do what I did and feed each amp with a dedicated 240 volt/15amp direct run from the service panel (and all copper busses is a must in my opinion), it is simply incredible how smooth things can get, not to mention even more output power.
I have a very well regarded Class A/Ab amp and I have done a lot of comparisons with all kinds of music; hands down the M1 Class D just blows my A/Ab amp out of the water and my brother who is a professional video/audio producer with a ton of experience with music completely agrees. BUT, amps like the M1 are going to set you back $7K, they are not inexpensive! However well worth it. Not to mention they only use 3 watts in standby mode and 13 watts in idle. And they never get warmer than a cool cup of coffee to the touch.
If you spend the money on well engineered Class D, you will never go back to A or A/b and certainly not Tubes in my opinion :)