If you want the best preamp for 2-channel music listening, then buy the 2-channel pre that sounds the best to YOU in YOUR system. I personally recommend Conrad Johnson Premier 14 or CAT.
Whatever pre you decide on does not need a pass through to work for HT. Just connect the left and right front outputs from your MC-1 to any input on the new preamp, calibrate the system for HT use with the preamp set at a repeatable volume setting (a numerical display makes this easier). When you watch a movie set the volume on the preamp to the setting used during calibration, and use the MC-1 to control the system volume. When doing the 2-channel thing the new preamp controls the system
This is how I configure my system (for HT the CJ is set at 72, which happens to be its “unity gain settiing), and it works great. I can see how a pass thru would be slightly more convenient for HT use. But for you, and me this will limit your choices with regard to preamp. If the pre you like BEST happens to have a pass through then you get the convenience; if not then make your choice for the best 2-channel sound.
Whatever pre you decide on does not need a pass through to work for HT. Just connect the left and right front outputs from your MC-1 to any input on the new preamp, calibrate the system for HT use with the preamp set at a repeatable volume setting (a numerical display makes this easier). When you watch a movie set the volume on the preamp to the setting used during calibration, and use the MC-1 to control the system volume. When doing the 2-channel thing the new preamp controls the system
This is how I configure my system (for HT the CJ is set at 72, which happens to be its “unity gain settiing), and it works great. I can see how a pass thru would be slightly more convenient for HT use. But for you, and me this will limit your choices with regard to preamp. If the pre you like BEST happens to have a pass through then you get the convenience; if not then make your choice for the best 2-channel sound.