Tube Preamps.....

The Schiit Freya is maybe a giant killer of a tube preamp, and it's so cheap you could add an astonishingly great DAC and stay in that budget.

Another vote for the Freya. At least give it a try. For $700 bucks with a 15 day return less 5% restocking fee (and shipping) you will risk little.   It’s a very flexible, balanced design with (tiny) remote, several output modes (one of which is 6SN7 tube-based) and numerous inputs. Also has a very very good volume control and 5 year warranty.
I know...it doesn't cost enough so it must be junk. Why not let your ears decide?  

You could do Freya + Gungnir MB or even the Yggdrasil DAC at your (stretch) budget. Lots more info over on HeadFi (Freya impressions and tube rolling thread). Good luck.

http://www.schiit.com/products/freya

https://www.head-fi.org/threads/schiit-freya-impressions-and-tube-rolling-thread.832177/

Note that the only serious issue with a Freya is the fact that you could become obsessed with 6SN7 tube types…my SE power amp also has one of these (a NOS Amperex), so I seem to now have a tube collecting problem with the Freya original 6N8S tubes (which are possibly all you need), Sylvania "chrome domes," more NOS Amperex when I can find them, new version Tung Sols (not too shabby really), and more coming from stashes of NOS RCAs and on it goes. You've been warned.

If you can live without a remote, I recommend the CJ Classic tube preamp. Used ones show up on Agon all along with very attractive pricing. I’ve owned PrimaLuna and I consider this a (significant) upgrade.