It's not hard to run two cards in DOS at the same time. You don't even need any resident drivers depending on the cards you have, just an autoexec.bat "mixer" program that sets levels the way you want them.
My favorite setup in the 1990s was a Sound Blaster 16 ASP with a wavetable daughterboard (for general MIDI) and a Gravis Ultrasound (for my demoscene work and for games that supported it). I had the output of the Sound Blaster plugged into the LINE IN of the GUS, and the GUS mixer was set in autoexec to enable and turn on line in. I then connected the line-out of the GUS to my speakers. It worked great as long as I wasn't stomping on any other card's IRQs, DMAs, or ports. IIRC, I believe I had them set to this:
Sound Blaster 16: port 220, IRQ 5, DMA 1, HDMA 5 -- with GMIDI using port 330 (the default)
GUS: 240,7,7,7,7 (port 240, IRQ 7, DMA 7)
This was the most compatible setup across the widest range of games for me. It works fine as long as you don't try to play sound through the GUS at the same time you want to send something to a printer, as both in this setup use IRQ 7.