If you are going to get the Oppo I would suggest using the analog multichannel output on the Blu-ray player to connect to the receiver. The PS3 is not capable of such a connection and it would be a shame to get rid of such a reliable/solid receiver just to be "up with the times".
The Oppo can decode HD audio internally and put it out over the analog outputs. With your current setup there is NO other way of getting the full potential out of Blu-ray's sound codecs. If you use Optical or Coax you are getting bare bones Dolby Digital, DTS, and 2 channel PCM as Digital Rights Management has decided to not allow any HD audio to be passed of SPDIF type connections, even if it is theoretically possible.
Go with the Oppo, get some sets of RCA cables (or better two sets of component video cables which are guaranteed to be 75ohm and they are color coded) to connect your Oppo to the B&K.