I also run a dual purpose AV system but have found that there is no way an AV preamp sounds as good as a dedicated audio preamp.
I have listened to my system both ways, using my video amp - Marantz AV7702 Mk 2 (the last unit they had that allows proper setup for a really good home theatre - your 8802a is a more expensive unit of the same generation) into a Roland 5 power amp.
I switch the speaker cables over to my audio pre/power to do serous listening to music and the sound is significantly better. You might consider trying out a different preamp with your existing power amp and see what you think.
I'd agree with the Black Cube as an affordable phono stage that is priced very reasonably. If you do that, do report back on how it compared with the Marantz (maybe you can borrow a demo to try before you buy).
I have listened to my system both ways, using my video amp - Marantz AV7702 Mk 2 (the last unit they had that allows proper setup for a really good home theatre - your 8802a is a more expensive unit of the same generation) into a Roland 5 power amp.
I switch the speaker cables over to my audio pre/power to do serous listening to music and the sound is significantly better. You might consider trying out a different preamp with your existing power amp and see what you think.
I'd agree with the Black Cube as an affordable phono stage that is priced very reasonably. If you do that, do report back on how it compared with the Marantz (maybe you can borrow a demo to try before you buy).