Looking at the 505 user manual, it seems that your receiver does not accept Multichannel PCM via HDMI, so I'd go with the Panny DMP-BD55 to get the 7.1 analog outputs. Half of the draw of Blu-ray for me is enjoying the TrueHD and DTS-MA sound modes, so I wouldn't miss out on them if I were you. In my opinion, everything sounds tighter and more detailed with the TrueHD/DTS-MA tracks compared to DD5.1/DTS/etc.
As for a 5.1 vs 6.1 vs 7.1 setup...most Blu-rays are coded in discrete 5.1, meaning you probably won't get much use out of that rear channel. I don't think your receiver can matrix a 5.1 to 6.1 when it is in Multichannel mode. However, if you are watching a DVD you can always go into the BR player menu and set it to bitstream (if you have it hooked up with an optical cable as well) and then your receiver would matrix regular DD5.1/DTS to all your speakers.
The multichannel inputs on your Onkyo will function fine with a Blu-ray player. They don't care if you have it hooked to a BR, DVD, CD player, etc. as long as it receives a signal.
In my opinion, get the BD55 and then hook it up with both the analog outputs and the optical output so you can go between PCM and bitstream output (in the BD55 menu) for BR vs DVD.
I'm relatively new to the whole audio entertainment system, and have some confusing questions that I'm hoping some people can help me out with. I have the Onkyo TX-SR505 receiver, and currently have it configured with a 6.1 setup. I'm looking to purchase one of the two Panasonic Blu-ray players, but am not sure if I should invest in the more expensive 55k for the 7.1 analog out terminals, or stick with the cheaper BD35k. As a point of reference, the SR505 has HDMI, but as pass-through for video and audio. So that means I can only connect via optical, digital, RCA Stereo, or 7.1 analog multi-channel. So here are the questions:
1) Will I notice a difference with either TrueHD or Master Audio over Dolby Digital Ex, or DTS Digital Surround? (TrueHD and Master Audio are over the analog outputs; the Digital Ex, and Digital Surround are over the digital outputs).
2) Since I have a 6.1 setup, should I still be concentrating on a 7.1 setup, or on a 5.1 setup? Or is the Onkyo receiver smart enough to detect the signal and adjust it accordingly to fit my 6.1 setup?
3) Will the analog multi-channel inputs on the back of the receiver act as a pass-through of some sort, since the Blu-ray player would be doing all of the audio decoding itself? Or am I assuming too much? The Onkyo manual states that that the multi-channel terminals on the back of the receiver are designed for DVD players with SACD and DVD-Audio support. So I'm curious if it will still work with the Blu-Ray
Thank you to those that chose to stay and read my lengthy email. Any elaborate insights are appreciated