[rabbitc]

I think you're stuck there, blu...
Trying to marry legacy stereo equipment with new digital theatre never has a happy ending. A new receiver is the only way forward, I'm afraid. Component video will be satisfactory for gaming, but if you have any intention of watching blu-ray movies, HDMI is your ONLY choice as it is the only connection that supports HDCP authentication protocol. (otherwise your movie is downscaled to 480p)

You should be able to do one of two things:
A) get an older home theater receiver that accepts 5.1 TOSLINK optical and hook up the audio directly from the PS3's optical out to the receiver. You will still be able to use the HDMI for video (provided your TV accepts HDMI)

B) get yourself an HDMI Home Theatre receiver that accepts HDMI sound (not a pass-thru) and you're in audio flavour country. As the PS3 internally decodes loseless codecs - you can bitstream the audio to an HDMI receiver with unbelievably amazing sound quality. My recommendation (good value for money) would be either an Onkyo TXSR606 or a Denon 1709 - both great boxes with top-notch audio.