best tube preamp under a 1000 for B&K 200 sonatas?

Be mindful of the output impedance of the pre.

Can you explain a quickly about the output impedance of the preamp? What should I stay away from? I have seen a few Carys on here in my price range.,also what about eastern electric min max?

You want the output impedance of a pre to be at least 10x less than the input umpedance of your amp, across the audible frequency band. To be safe, and since we often don't have measurements available across the spectrum, 20x is often recommended.

A nice used Quicksilver Line Stage would probably fill the bill nicely.

Hello,
I see a TAD 150 Signature posted on Agon. I owned one 4 years ago. A very nice sounding tube preamp for its price point. Has no short comings really - just sounds right. Has remote, only uses (2) tubes so tube rolling is not too costly. It has a phono section but to be honest it's not that good. The value here is in the line stage.
If you could get it for $775 I'd jump on it.

I also see a Mapletree preamp posted. Have not heard one though. I've read they sound great but they are not much to look at. That could be a great bang for the buck so to speak.

Good luck!!!!