I think your Projector won't benefit from upgraded video processing because it's a native 720p projector according to projector central .
Additionally HDMI is unnecessary see below for explanation.
RSP-1066 surround preamp-processor
Analog inputs: 8 RCA line-level (2-channel),
RCA (7-channel
(from
http://www.ultimateavmag.com/surroundsoundpreampprocessors/85/index2.html)
As you can see the oppo has analog outputs and your pre-processor has the inputs. To get HD audio you simply need to run RCA type cables between your blu-ray players analog out section and pre-processors analog in section.
Your oppo will process all the new formats for you and do as good of a job as anything else out there because they will use the best chips available to them at the price point. If you need additional HDMI inputs I suggest you pick up a manual switch at monoprice.com
In conclusion keep your stuff and don't look to upgrade. Unless you just don't like your rotel.
If you have additional questions feel free to ask.