Sorry Julie, my coffee hadn't kicked in when I replied - and I confused myself on the last paragraph
Again on the topic of Bryston, James Tanner is the source to go to on questions about the specific differences on his products, future plans, upgrades etc. It's not very often we get the opportunity to have direct access to this type of resource inside a manufacturer, and I would encourage you to drop him an email with your questions.
The caffeine is now flowing, and I can try and explain a little better how I integrated a preamp with no HT bypass in my system:
1. Take the front left/right processor outputs, that would normally feed the front left and right inputs of the power amp, and plug them into an spare input on the preamp.
2. Turn the volume down on the preamp and run the test signal from the processor.
3. Select the input with the processor source and slowly turn up the volume level on the preamp until you reach the target level you need (using your ears or preferably a SPL meter).
4. When the volume level is equal to the the other channels you simply mark up the volume level on the preamp - and this becomes the volume level you use in HT mode. Effectively you are manually setting the HT bypass level. To increase the volume when listening to your HT the processor volume is used, and the preamp level is a constant.
5. When you use the preamp to listen to CD's for example, you just use the preamp as normal with its volume controlling the sound level.