Thanks for the helpful feedback Great Hierophant. The good news is that I do have a Roland MPU-IPC and breakout box handy in the event I decide to get rid of the LAPC-I/MCB-1 (the reason the LAPC-I ended up installed to begin with rather than the MPU-IPC was because I acquired the LAPC first). If I remember right on how my MIDI configuration is set up, I actually do need the 2 MIDI OUT connectors as a minimum in order to use my Phat.Boy real-time MIDI controller in conjunction with the CM-500.
In response to your question about other MIDI modules I plan on using with the PC, actually fortunately I think I'm all good with what I have now

Between the CM-500 and the Sound Blaster, I have everything I need for gaming, and although admittedly not on the scale of the SC-8820 or SC-8850, enough to keep me happy enough when occasionally dabbling on the MIDI music side. Before the CM-500, I had tinkered with both the LAPC-I and SCC-1, but the CM-500 removed the need for these except as a spare MPU-401 interface.
One other question for you: how large would you say the difference in sound/quality is between SC-55mkI and SC-55mkII? Would there be any web-based samples you could point to for comparing the difference between them?
What I would do if I were you is to buy a Roland MPU-IPC or MPU-IPC-T and sell both the LAPC-I and SCB-55 + MPU-401 cards (the second advertise as an improved SCC-1.) That way you could still have a Roland MPU-401 interface with two midi outs. (I wonder if they make \"midi splitters.\") Your net profit will be well worth it.
The real disadvantage of the CM-500 vs. the SCB-55 is not the lower number of patches, games don\'t really use extended GS patches. The disadvantage is the lower polyphony, because the CM-500 hardware can only output 24 simultaneous voices vs. 28 simultaneous voices of the SCB-55 or any other SC-55mkII offspring. Midi composers back in the day found that 24 voices were not really a lot of voices, even the AWE32 can boast 30.
What other midi modules are you using or plan to use with your gaming PC?