Many, many preamps have an HT bypass, the advantage of the Parasound 2100 (and the P7, even moreso) is that it was designed to optimize the use of the HT bypass while all others, that I know of, merely accommodate the passthrough.
Among its relevant features (quoted from Parasound) are:
Connect your 2 channel analog sources to the Model 2100 instead of to your surround receiver
Connects to surround receivers L, R, Sub line out jacks & to power amps input jacks
Blends seamlessly into surround system, automatic pass-through when turned off
Bypass input can be selected by remote
Creates a mono sub channel output for 2 channel analog sources
Analog bass management, low pass filter, adjustable 20 Hz - 140 Hz
Separate output jacks for full range (large speakers), 80 Hz high pass filtered (small speakers)
Kal
