Phil's early reviews of the Vortex, and the fact that having a PCI card that actually worked in DOS at the time was pretty rare (most PCI cards were not much tested) meant Vortex enjoyed an era of overhype. It is still one of the better Windows sound cards to play late 90s games on, but for DOS it is just junk, even for a PCI card.
Here, have a listen to Phil's Vortex 2 DOS recordings:
Aureal AU8830 PCI FM Synthesis
Then compare with my Fortemedia FM-801 recordings:
Fortemedia FM-801 PCI FM Synthesis
Neither is genuine OPL3 FM but the former is complete garbage compared to the latter, and they are both cards that work rather well in DOS.
Of course, Vortex supports A3D and FM-801 does not, and so as with all sound card choices one has to make in this hobby, you have to pick your poison..