Highest value pre under 1.5k used?

Easy, the Topping pre90 ($500) + Ext90 ($250, optional). Look at the preamp used by this Stereophile reviewer,

Perlisten S7t loudspeaker | Stereophile.com

I have the same preamp and it is great with the Benchmark AHB2 (also good with Parasound A21+). It had some volume issues with a few other amps I tried it with. 

A Benchmark LA4 preamp which may be available at a used price of $1500, a new one is $2600. It sounds exactly like the Topping pre90 but it works perfectly with all amps I have used with it. It also has better features than the pre90

The Topping pre90 and Benchmark LA4 are preamps you use of you do not want the preamp to add to the sound.

Check out Aric Audio. He makes a tube preamp within your budget. He can configure it to your needs. Great guy to deal with.

Thank you everyone for the suggestions, I do have a Quicksilver but it is out of commission right now, it's an old 6dj8 version. It does sound very good when it worked. The Benchmark stuff is intriguing also, I am going to read more about the Topping. Thanks again!

So why not call Mike at QS and see about getting it repaired.... I bet its worth the cost to repair.

used rogue audio RH 5 linestage headphone amp.  stereophile class A.  hard driving transparent and energetic.