I hate to say it, but upgrading the arm of the RP6 to an RB880 or RB3000 (you sound like you're willing to throw a good amount of $$ at your itch) will really improve your sound and you will appreciate how much everything else sounds better. It probably would be worth it just to go to a P8. Arm makes the most difference though.
I had a P5, upgraded the arm to the RB880 and was blown away. Then I got the P8 because of a couple features and the sound also improved a little, but by no means nearly as much as the arm upgrade. I'm still glad I did it. I think the source improvement is the most satisfying. Also like VDH carts.