You need a few things:
- ISA bus emulation
- EAX
- A3D2.0
No one card does all that, and only a specific chip does the last. Ideally you would have a SB Live 5.1 for EAX and DOS compatibility, and a Vortex2 for A3D2 (which doesn't do EAX/DOS). As you have an ITX case with a single PCI slot, you are buggered for choice. Either build a second computer for A3D2 or build a mATX at least that you can stick 2 sound cards in - although you will need to play device manager wackamole every time you switch between them.
My advice - build a second system. This also gives you the option of using different variants of graphics cards. E.g. a popular breakdown would be a Geforce/Live! for D3D/EAX in one, and a Voodoo[35]/Vortex2 for Glide/A3D2 in another.