Is anyone aware of a 2 channel preamp....

I have an Outlaw ICBM-1 that I am not using and maybe time to sell. Might get close to where you want. 

Forgot to mention, read the docs carefully. The P7 has bass management, but in HT mode, it disables it's internal bass management in favor of external.

So you know, the 2 sub out is usually just a convenience. It is not usually electrically superior to using a Y-splitter.

Parasound has the P5, P7 (recommended) and now the NewClassic 200

http://www.parasound.com/200_Pre.php

I also think the Zpre has a dedicated HT bypass input.

Best,
E

Outlaw Audio RR2160 Stereo Receiver

Not a preamp exclusively, but appears to have the features you are looking for, albeit in a 'receiver':

https://www.outlawaudio.com/products/rr2160.html