Best 6NS7 Preamp for a Pass Labs XA25 amp

I also have the Aric Audio Motherload preamp with phono stage and Dueland caps. I have been very happy with it.

+1 for Aric Audio.  I have the xa25 with an Aric Audio Unlimited preamp.

Atma-sphere MP1. Any version. Balanced or rca option. Both excellent.

Linear Tube Audio manufacture 3 magnificent preamps that can use 6N7. They are delivered with 12N7's but by moving a jumper on the pcb you can change the heater powersupply to 6 volt and then use the mores expensive but cool sounding 6N7 tubes. The MZ2 with our without your remote should be within your budget? www.lineartubeaudio.com

You're not going to find a better 6SN7 preamp than the SP14 from VTA.  You can buy it either as a kit, or preassembled and fully tested.  You can even get custom builds for a bit more cash.

Complete kit is $950
Fully assembled & tested is $1450

http://www.tubes4hifi.com/pre11.htm#SP14

The base SP14 looks pretty plain, but some of really don't care.    Don Sachs will do a custom build for you of this preamp.  Pricing will depend on just what you're asking for.