Switch from AB to D

I have a Onkyo TX NR 3007 that eats up electricity because of 4 amps inside. I would like to switch to the Vidar class D from Schitt's. I really like what I've read about it and the reviews. I am handicapped and can't get out to listen to any class D units in my area so I'm going to depend on some people here give me a good idea where I'd be going from class A B to class D what's my sound. I will be using the Vidar with a Audio Experience Symphony preamp with three matching Telefunken tubes that have been in there since I bought it and it's serviced me well along with an Audio Experience Concerto Plus phono preamp. I have an older Soto Sapphire turntable with a clear audio virtuoso cartridge wooden body that has been rebuilt by the soundsmith what a great sound. Oh by the way I have an Oppo 103 Player for my digital along with PSB image five speakers which I got for a great deal of many years ago and they still sound good with my system.
So the bottom line here ladies and gentlemen what am I going to experience putting a Class D amp with a hundred watts per Channel in place of my Onkyo with 140 watts per Channel at class A B power?
Thank you much
Ron in Highland Michigan
A/B to A/B is apples to apples. The Vidar will blow the Onkyo away. See how it sounds with your old preamp. And when you get a good excuse, audition the Schiit Freya+. 15 days to decide whether the Freya is enough better than your old pre to justify the $900. I'd totally forget about Class D for the moment. Maybe someday a D-powered sub. Many good ones to be had for not much $ if/when you get to that point. 
I've been very happy with an Ncore Class D diy kit, but also with the Nuforce STA200 which is class a/b.  Both can be had for about $500, and in conjunction with a Schiit Freya, sound heavenly.
I’ve been researching integrated amps, and the name that keeps popping up is Rogue Audio, particularly the Sphinx. I’ve not yet heard it, but plan to audition the v3 in the near future. In many of the reviews and comments, people seemed generally surprised with the sound that’s been achieved with a tube preamp and class D amp and crediting the engineering.  
I have had several class D amps over the years. I don't agree with all of the "not ready for primetime" feedback. Your price range is a limiting factor, but I would look at a used Peachtree. 
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 :)