Single Status Update
Finally got the DOS sound card drivers working. The version of the Aureal Vortex Advantage I bought was some no-name version whose included drivers disabled the MPU-401 for some stupid reason, forcing me to remove them and install the reference drivers, and I had to disable bus detection in the .inf or the drivers would complain about being plugged into the secondary PCI bus and refuse to turn on the SB Pro emulation or the MPU-401. But it finally works, I've finally got Doom running in its full glory.
(the wavetable synth in the Vortex Advantage sounds like shit though!)