As a long time (>20 year) user of and believer in passive line stages / removing active line stages, the answer is a big "it depends." I.e., it depends on the output impedance of your source, the overall quality of the output stage (including both volume control mechanism and current delivery) of your source, the capacitance of your interconnects, the input impedance and sensitivity of your amplifier, and (of lesser importance) the sensitivity of your speakers. Beyond that, I don't see enough information about your components and system to give a more definite recommendation. I own an older Oppo (BDP-83se), but don't believe it has output volume control; however, my general impression is that I don't think the output stage is of the quality that I would necessarily prefer a direct drive sound. By contrast, some of the aftermarket Oppos that significantly upgrade the output stage are suitable candidates for direct drive to the amplifier.
Should I eliminate my preamp?
I have been using my Audio Research tube preamp and Bryston amp to drive Magnepan speakers for years. Recently I added a Oppo blue ray player to my system and connected directly to my amp using the balance cables. The reason was to eliminate the signal having to go through another piece of equipment before it hits the amp. Am I wrong or what am I missing?