Line level attenuation - active preamplifier

Question/advice requested. I have used up all my analog outputs from my C-J MET-1 (5.1ch) preamp to my amplifier for my HT system (other than Tape-In/Tape-Out circuit) and would like to set up an additional system with a 2ch amplifier & speaker for use with 2ch music but would still like to use same preamp to prevent purchasing another . I was thinking of using the preamp line level Tape-in/Tape-out and think I may have 2-3 options and was looking for some Tech knowledgeable feedback for pros/cons with a focus on maximizing listening experience.
Option 1) - Use my source volume control (ie Oppo  BDP105D) to reduce to a low level signal before my preamp 'Tape-In' and allow line level gain in my preamp before 'Tape out' to my 2ch amplifier. I am a little concerned that by reducing the input signal before the preamp I may impact overall listening quality not to mention screwing up something in my preamp by asking it to provide line level gain however I cant imagine it would be a problem as they wouldn't have given Tape-In/Tape-Out as an option if it was ?
Option 2) - Use my source with a higher (or even max) volume control and then add attenuation (volume control) after the preamp Tape-Out by adding a passive preamp between the preamp and 2ch amplifier. I am a little concerned that I am asking my original preamp to work hard with max line level gain thru Tape-In/Tape-Out just to attenuate it again before the amplifier hence impacting listening quality ?
Option 3) - Forget altogether using the Tape-In/Tape-Out and just add an RCA switcher on the original L/R preamp outputs to select use between my HT amplifier and my 2ch amplifier. I did try using an RCA splitter but it caused ground loop so would definitely need an RCA switcher that isolates each signal path to its specific amplifier. This would probably be the simpler option as i could then use the preamp volume control for both amplifiers independently of each other. I would ask for any suggestions on good quality RCA switcher as I only see cheap RCA switchers which I presume would defeat the whole purpose of having good interconnects ?
I have also heard about being careful with impedance but I don't really understand if this is a problem or not with any of the options above. thanks in anticipation of replies !