Electrostatic Speakers/SS amp - what tube preamp?

AE3 by Cary new/used still will be under your budget. Make sure that your poweramp input impedance is >=30k.

On Audiogon: Rogue 99 magnum for $1500 or Cary 88 for $1200 would be your best choices. If you're looking at an AE-3, from experience, the DJH version is a big step up.

Considering your use of a balanced DC coupled solid state amp with an input impedance of about 50 Ohms(?), I think the the well built, user friendly, flexible, balanced, low out put impedance, DC coupled, neutral sounding, Sonic Frontiers Line series make ideal candidates.

I will second the SF choice.The SFL-2 is much better than the SFL-1{not sure where Sig.version comes in}.Possibly,the terra Song SS-1 or Marsh P2000.Are you using digital or analog.Digital always sounded better using this amp than did my 46K analog set-up.You will want something with a little sparkle up-top.