Best 5.1 McIntosh separates

It will cost you $600+ just to retube a Mac amp. Maybe look at Proceed or Lexicon or Anthem or Rotel separates. You may be able to get a good 5.1/7.1 pre pro and a warm sounding 5 channel amp combo here on the Gon.
As far as Mac goes, I would forget it unless you increase your budget significantly. Newer gear from the above mentioned brands may sound better than the really old Mac gear that may fit into the $2000 budget. I am not trying to steer you away from Mac (I am a proud owner of tube pre and mono blocks), it's just that Mac ain't cheap, and their gear tends to hold their value fairly well over time--meaning that even the older gear is not inexpensive.

Thanks Cajunpepe!

How does Cary Audio Tube Amps stand against the one you recommended? Any specific models to look for?

Again, champagne taste on a beer budget!!
Cary tube amps are not inexpensive. I believe the v12/i/r amps at 120/60 watts still command at least $1500+, and those have not been current for some 4-5 years. And that only gets you a stereo amp. You will need 5 channels, not 2 if I understand correct.
Go for a Proceed 5 channel amp here on Agon. They sound fantastic for the money and can usually be had in the $1000 range depending on power (5x100/125/200).
Have you noticed that there are not many (Butler audio comes to mind) 5 channel tube power amps on the market? Most folks reserve the yumminess of tubes for critical listening through a dedicated 2 channel system. I use the high end Macgear for 2 channel and use a Rotel stack (RSP-1068 pre/pro and 5x125 power amp) for my TV and theater and use the theater bypass on the MC2300 preamplifier to pass through. It works beautifully.
BUT...if you are still hell bent on a 5 channel tube amp, look at Butler Audio. They sometimes come up here on the Gon and may be had for your price range.
BTW, the Butler gear is very easy on the eyes. They also make tube amps for car audio...sweet.

After reading various threads, I'm no longer hell bent on 5.1. Stereo seems like the way to go.

So considering the above price point, any advice on make / model?

Ho much of a difference a dedicated Tube Pre-Pro will make compared to using the Pre Outs from SS Kenwood VR-4090 receiver?

Thanks for your time!

I can't recommend a home theater with tube amps. Tubes take time to come up to operating condition. A theater needs instant on. You don't want to miss your sound if you dash for a show. Also five (5) tube amps will get toasty in most rooms. If you run a fan to cool the room you increase your noise to sound and lose quality.

Tube amps also diminish in power and performance with time played. All 5 amps might have different output after a years use. That will definitely affect sound track balance.

Lastly, you will not get that fabulous SLAM factor with tubes that you get with solid state. Tubes just are not the right tool for the job in my opinion. How do I know this? I did a theater with a McIntosh MX136, MVP861, and five (5) MC275 tube amps in mono. Looked cool, was hotter than hell, and sounded flat!

Have fun!