Hdmi will always be identical to or better than optical. The analog output of the oppo will measure better than the output when processing over hdmi, but it's arguable if it's audible.
HDMI will make for the cleanest setup possible, and the highest quality (with possible exception listed above). Sony bluray players work just fine, as for picking the AVR I'll defer to others but you should be good with any yamaha, denon, onkyo, or marantz that has all the features you want.