How to? Add a Pre/amp for 2ch to a HT receiver

I currently have a B&K 202, and it is fine, but I am looking for better 2ch sound. I would like to use a tube pre, and a separate amp, but the trick is I would like to use my main speakers (currently Vandersteen 2Ce's) for both the HT, AND the 2ch setup. I have noticed that some pre-amps (e.g. Rogue)have an HT bypass loop- how does this work? Does it affect the sound quality?
The pass-thru bypasses the circuitry and volume control in the preamp. You should also be able to use the tape loop.
Yes, the "pass through" has no gain, so it just gives your amp whatever showed up at the input. This is useful for setting the level controls of your pre/processor so you get consistent results. Plus there is less distortion since you bypass the vol. control on the preamp. You will however be feeding the same amp for 2 ch and for 5 ch., so you will probably want a 2 channel amp and a 3 channel amp.