I too do this.. I set my Quad 99 Preamp to a level of 20 everytime I wanna listen to HT. Gotta remember to turn it down to 10-12 range for normal 2-ch listening, otherwise my neighbors get quite a suprise.
I had to spend some time with a spl-meter to level match my Marantz 5400 center and surrounds to the preamp+amp 2-ch setup.
FYI.. the Quad kills the Marantz when it comes to 2-ch music, that why I kept it, it's not even close.. and the Marantz is known for being WAY more musical than the likes of Denon/Yammy/etc.. funny thing though, when I run a 2-ch source through the Marantz's internal DACs then into the Quad it sounds pretty good, it just does some kinda magical goodness.. go figure.
hope this helps,
mike