HDMI cables vs RCA/coax for sound in a HT system

I am debating between buying the OPPO bdp-103 and the -105. My question is: for the audio alone, are coax cables (RCA) better than HDMI--or doesn't it matter? I have Aragon 8008 and Aragon 8008x3 amps, Rotel processor, PSB Image speakers, and am making the move to blu-ray for the first time. I want to make sure I get the best possible audio in addition to great video. Will HDMI give me as great audio as coax cables if I play both Blu-ray Discs and cd/sacds? Or should I be planning to use HDMI for the video and RCA/coax for the audio? Haven't been able to discern a clear answer from other previous postings. Thanks!
This depends upon wheteher you wish to use the Oppo for decoding the digital information or your Rotel processor. I would probably opt for using analog cables thus making the Oppo the decoder of the digital information...

First Buy The BDP-105 Better Audio. Then Try Both HdmI & Analog Outputs. Let Your Ears Be The Judge.
Thank you both. If I go the analog route (using either the 103 or 105), will I be able to play DVD-Audio discs as well?

I read somewhere that I needed to use HDMI for audio because digital coaxial will not support SACD at all, that DVD-Audio will be stereo only, and that Blu-ray will be standard Dolby Digital and DTS and not the high resolution Dolby Digital TrueHD or DTS-HD Master. Is this true?

Many thanks again, Ashley
You can use either HDMI or all-analog outputs for all these formats.
Just make sure your Rotel processor has multi-channel inputs to connect to your Oppo.
Wonderful--thank you all!