It is a good idea to purchase a vintage tube pre-amp.

I loved my old MFA Magus. Not in good repair at the moment but when it was good it was very good. I'm looking to sell it if someone wants a worthy project. Or I'll get it up to specs and then sell it. I had issues with my power amp so switched to an integrated to simplify my electronic life. 

I previiously had an Audio Research LS26 which sounded superb.  Plus it is both single ended and ballanced.  Should be able to get a good used one for around $3000.  Can not do better for the money.

I have a Zesto Leto just like the one listed here on Audiogon. You can run it balanced or single ended. It's not the euphonic tube pre of vintage make but the company makes first rate electronics. The output impedance stays low so a long run to your amp is not a problem. It's on here for $3500 but you may be able to bargain. I have high efficiency speakers and you can turn it all the way up, dead quiet.
I paid a lot more for mine and would buy it again. 

With your budget you can pick at the top of the heap if you are willing to go a little older.  ARC SP-10 or SP-11.  While they are harder to find, there are even CAT SL-1s available in your price range.  I bought a used CAT SL-1 over 25 years ago and have never been tempted to upgrade it.  In all those years I've only had to replace one cap in the power supply.  Ken builds them to last.