The 82C931 is supposed to have a craptastic OPL3 clone. The older OPTi chipsets usually come with discrete OPL chips and they are usually OK.
I think this one is fine enough as long as you want to use General MIDI, and doesn't have the hanging note bug, in case you are having trouble with that. You could even put them in the same system, and disable most of what you can of the OPTi (except MPU port), leave the card in WSS mode, mute FM snthesis and run its line out into the SB16's line in to have the best of both worlds.
If you are not interested in using daughterboards or external modules... I'd skip it.