Hi Asher,
JohnK answered your question (on upsampling) exactly as I would have (thanks, John). As to your question on possible problems with the Oppo's internal bass management, I've never tried it, so there may be some lack of flexibility on that score--it's not uncommon to find limitations in the internal bass management of SACD/DVD-Audio players.
(by the way, what does "RB" stand for....sorry, I'm not up on all the acronyms).
As far as "discernible improvements" go in the audio playback qualities of CD, DVD-A and SACD players, if you use music rather than test signals (in a lab bench test), it's impossible in my experience to detect any discernible or audible improvements between well-designed players, no matter what the price or how exotic the upsampling circuitry is--provided the comparisons are conducted as I've described previously with duplicate discs running in sync, etc.
Regards,
