AMP or Preamp

I agree with the others that your speakers are not reaching there full potential with your current amplification. There are many good choices with different benefits. I have in general found separate amps and preamps superior. MacIntosh  offers high reliability, long tern serviceability, and good resale value. However I have not found their audio performance a good value. The suggestion to try a local dealer is likely to provide a lot of good choices

Hear the Wilson and Audio research and is good combination (tube amp).
also fans of Pass labs (solid state)
If space allow go separate for amp and pre .
Cheers 

@davekay

I would start with amps first. 2 large mono blocks and 2 mono block tubes. Once you have your base , go for a preamp that best suits your needs. A cherry on top sort of speak.

He only wants to spend $5K-$7K.  It seems that a used integrated would be the way to check all his boxes and find something worthy of those Wilsons.

I have not heard a set of Wilsons like you have before - but I’ve heard from associates on other forums that the’re awfully nice / revealing.

It sounds like you already have some pretty decent sources, and the Power Amp that you have could be better, but it’s no slouch either.

If I were being "semi-practical" - looking for high quality, but VALUE = I would be looking at some of the BHK Signature products from PS Audio (Hybrid Tube / Solid State - taking advantage of the properties of both in a "synergistic" combination) Maybe start with the Pre and upgrade to a nice pre-owned set of monoblocks to replace the Rotel Amp later.

Another two decent brands to try for Pre-Amps (Line-Stage) would be Audio Research and SimAudio Moon -
I have heard a local high-end dealer’s demo system - with Vandersteen Model 7 speakers being driven via Audio Research Reference tube components and other goodies. (That was a system in excess of $100,000 retail) The imaging and black levels were almost "spooky" - but for that kind of moolah, they SHOULD be!
The solid middle-of-the-road Audio Research stuff or older, refurbed Reference stuff might be attainable

But with a system like yours and the amount of your budget - I would certainly:
-Audition a few units, to see what sounds best with the rest of your Sys
-Only buy from places with a good Return Policy, so that if you don’t like the way it sounds, you can return it for a (at least nearly) full refund.
-Find a forum with other Wilson Speaker owners, and see what has worked for THEM.

If you want to keep the system "sleek" = minimize the number of boxes to be interconnected, I have it from a reliable source that I trust (a different local HiFi dealer who carries a wide range of price options) that the Hegel integrateds are awfully nice.

Good to hear that you did whats absolutely right. Started with the speakers. I would be careful spending a lot of pre/amps to begin with. Buy some cheap and good class D like XTZ Egde. Then you have power enough. See how you like it. Don’t need a pre to the Vault. The next is your room. Adding a professional room correction unit would make wonders to your overall sound. And will also educate you in sound/listening. No speaker presents a correct frequency curve in a normal listening room.