Integrated Amplifier for B&W 803 D3

Not sure I’d try to drive the 803s with tubes unless you listen at fairly low volume levels. A nice compromise might be a good Class-A integrated. There are some Gryphon Diablos available here now, but I’d probably go for this Vitus SIA-025 that originally retailed for $27,000 and will likely pair very well with your speakers.  Honestly, it’s hard to see going wrong with an amp of this caliber.  

https://www.usaudiomart.com/details/649766445-vitus-sia-025-mki-integrated-amp/

For subs you can get a pair of excellent SVS SB2000 Pro subs for only $1500, and you have a generous, risk-free trial period to make sure they work well in your system.  Hope this helps, and best of luck. 

You might find the Circle Labs A200 interesting. It's a novel hybrid design (NOS tube pre paired with exceptional quality SS amp) that sounds alive.

Here's a recent review in Positive Feedback: https://positive-feedback.com/reviews/hardware-reviews/circle-labs-a200-integrated-amplifier-thank-y...

Heads up that I import Circle Labs products into North America.

You want to spend a total of $2k on the subs? So $1000 each? If so the SVS Pro 2000. They come both seal and ported and have a 30 day trial.

But the 803s deserved better subs. Good subs can make a system but bad subs can break it. JL Audio E line is very good budget option but I just can’t recommend them to anyone as mine have broken so many times. Lot of good subs out there to choose and I would wait until you have a bigger budget. 

For amps, I alway like McIntosh with B&W. They make a few right around your price range. The MA12000 is a tube pre with 350 watts of solid state. But $14,000.

 https://www.mcintoshlabs.com/products/integrated-amplifiers/MA12000

Video because this forum needs more eye candy. 
https://youtu.be/y_JTrdYDPHg