Preamp recommendations for my system please

Why not a "plain" Ref 6? That can be had for under 10K. Snagging a 6SE at that price point is...optimistic. I’ve moved on from my Ref 6, to a VAC Master, and yet I still admire the 6. It’s really a matter of system matching and personal preference as to which is better. The Master is unabashedly tube sounding - in one of the most resolving and beautiful implementations possible for that path. On the other hand, the Ref 6 straddles the line between traditional top tube and top SS sonics very successfully. Because of that, it can match nicely with different amplifiers. I had to work a bit more to start tapping the Master's potential in my system. 

Rafael Todes reviewed the Townshend Audio Allegri Reference for www.stereonet.co.uk and he uses the Bartok. He performs with the Allegri String Quartet. I believe he subsequently bought one for his own system - I've had mine for just over a year and am delighted with it. No expensive mains lead required and built in seismic suspension, it appears to fit your requirement for two XLR inputs plus balanced output. I prefer balanced to power amp. It needs some time to bed in due to the copious use of Townshend's Fractal wiring internally.

Call Roger sanders.

he will build you what you need"

the best, clearest, most honest preamp I've ever see. 
 

2nd the Onkyo p-308, if can find a good used unit, worth the price.  %1000

i still use mine in my 2nd system with odyssey kismet monoblocks, Rotel, rdv-1040. 
BIC V830's. Greatb2ndnsystem!
 

To my favorite poster on this thread. Thanks for the comic relief.

Better to Remain Silent and Be Thought a Fool than to Speak and Remove All Doubt