IMHO, you should keep the 60GB PS3.
Ask yourself, "What's the advantage of bitstreaming Dolby TrueHD and DTS-HD MA when my PS3 decodes these formats and sends up to 7.1 lossless PCM to the receiver?"
The only difference there will be is that instead of the conversion of the HD audio codecs to LPCM will take place in the receiver instead of the PS3. The receiver's DACs are still used and all other post processing can still be fully utilized with a multichannel PCM sound track.
Another cool bit is that the 60GB PS3 plays SACDs, the Slim version does not. Many DVD-Audio discs include a DTS 5.1 track. I personally was never able to differentiate between the DTS or MLP Lossless tracks on these DVD-Audio discs. I'm not saying there isn't a difference, but you can still enjoy the delights of a well mastered 5.1 audio recording with a very good lossy codec.
The best part about my plan is that it saves you from getting an Oppo or new PS3. This allows you to allocate those funds to the next upgrade you were considering. New subwoofer in the cards? How about some acoustic treatments?
Edit: Through reading your other posts I see you got your sub fix already.