Tube Preamps.....

Don Sach's DS2 6SN7 Tube Pre-Amp; own one and love it!

Wig

Another note on the Freya...it's much less expensive than many of the preamps noted here (about half the cost of the least expensive others noted), has more inputs both single ended and balanced with balanced outputs, and it has the cool 3 way passive/FET/tube operating options which can be changed with the remote from the beer soaked couch you got from your mom (or in my case, the throne I use since I'm Lithuanian royalty). I also found that the Freya really comes into its own with great tubes. I really think if the Freya cost 2 grand it would garner more respect immediately, and if more people said great things about them I'd feel better and less defensive about using one. 

Audible Illusions.....I have a M3a w/6H23NEB tubes and the new Aragon 8008 amp driving Magnepan 3.7i, SWEEEEEEET, to say the least. The M3b is even better!!!

I love my Eastern Electric Linestage pre-amp. You would have plenty of money left for the DAC.
Point to Point wired, exceptional build quality, nothing else comes close for the money.

I haven’t heard the Don Sachs but it looks nice plus he’ll work with you on upgrades to my understanding, a big plus. I have lived with a 6SN7 based output tube preamp up to a few years ago, still have it but it doesn’t hold a candle to my Bill Thalmann upgraded Vintage CJ PV9a in any parameter of performance. The Classic 2 SE with the teflon caps used, no longer available new is killer for the money and beyond but no remote, definitely worthy of consideration.