This would depend on the quality of the BD player. For example, the Oppo BDP83 may be better than many AVRs, but most BD players that decode may be equivalent to the "average" AVR with analogue inputs. I would think in your situation, a BD player that decodes to analogue would be the way to go, if you don't need anything else at this time from your AVR. It's also a lot less money.Has anyone ever A/B'd a Blu-ray via analog (BRP decoded) versus a Blu-ray via HDMI (AVR decoded)?
In order to go to the nth degree, you would want to decode in the AVR, provided the AVR is also to the nth degree - say $1500+