Audiophile pre-amps with home theater pass through

I am aware of conrad johnson and the new PS Audio pre-amps that have a theater pass through.
Does anyone know of some other quality pre-amps that have this the $2000.00 or less range?
BAT pres w/remote have a unity gain feature that allows them to be used is pass-thru mode.
Adcom GFP 750 (good) at about $700 =/- used, or Muse Model 3 Signature (significantly betters the Adcom) at about $2300 new (you will not likely find it used). The BAT SS pre amps like VK40 I believe have it, and the tube units have the unity gain as posted above - be sure to ck features on the specific model you are looking at. It is a great feature if you only have one listening/HT room.
Krell KRC-3, the S-3 input can be configured for unity gain.
Audio Reserch SP16 All tube too!
Proceed PRE is a good ss preamp w/ pass through and is selling very cheap used now since Proceed is being incorporayed into the Levinson line.
Can someone elaborate on what the unity gain feature of the BAT pre's is/does and how it relates to integrating a home theatre system into a two channel hi end system?

Kora Eclipse
To answer Scotty above, on my BAT VK-30SE you can set the relative level of any of the inputs wherever you want it and then assign that input as a "Fixed" input. No matter what you do with the BAT volume control the level of the fixed input doesn't change. Rather, volume is controled via your Pre-pro of choice.

In my setup that means I set all my home theater levels at my Accurus ACT 3. Center, surrounds and LFE go directly out to amps feeding speakers for those locations. L & R front channels are fed from the ACT 3 to my BAT, and it in turn feeds the 2 channel amps.

Voila! Home theater through the 2 channel setup, all the while maintaining the integrity of the 2 channel setup for serious music.
Sonic Frontiers Line 1 (~$1000 used) and Line 2 (~$1400 used). Both preamps are tube-based.
A little more money but ML380S is the best
I'm currently using a Classe CP-60 which has this function. The CP-60 model is discontinued now, but you should be able to get one for less than $1500 used.
You can also do this with passive volume control, I use Bent Audio 102 transformer volume control in my system.
McCormack RLD-1