Best Tube preamp under 2.5k Used

Sonic Frontiers Line series are excellent....you might one of them new in your price range.

Any Jadis preamp will be better than most any other brand at any price level. If the music is the most important thing to you, pick one up. There are several on Audiogon right now in your price range.

Sonic Frontier line 3 Preamp vs BAT5i which is best

For $2300 new the Melos SHA Maestro outperforms the BAT stuff and gives you the best sounding headphone amp in the world to boot.

CAT's are nice as a reference. Also Audible Illusions, and stuff from CJ, ARC, VTL. But if you really want to soften things up, get an old conradjohnson PV5. Not the most neutral, but wonderful for hard, electronic sounding stuff. About $500=$600 used.

Audible Illusions M3A, Period!!!

I've quite impressed with the vtl 2.5. I think they sell new for 1500. The vtl it-85 integrated 85 watt is very good as well. I have heard great things about the Audio Research 2's, and 5's. The 2 can be found used for around 1000. If you don't need a tube preamp, take a listen to the adcom 750. It is amazingly transparent in passive mode. I run it in front of tube monoblocks.