nightfallAs a starting point, I suggest you look for a tube preamp that has low output impedance, something below <1kohm (<1000ohms) 20hz to 20khz, as that will ensure it can drive comfortably any poweramp input, even if it’s 10kohm input impedance, without any added colourations, eg: fatness/thickness/thinness, slowness, rolled off.
Best Tubed Preamp For A Warm, Rich Sound, Yet Still Detailed and Agile. I do not want slowness, or lack of detail, however.
Then pick your choices from there.
You could even though it’s much cheaper than your budget, for a trial period try the Schiit Freya, remote control, passive, active s/s, or active tube, balanced or single ended, if you don’t like it you can send it back.
http://schiit.com/products/freya
Cheers George