I've got P5VDC-MX today so I've confirmed whether SB16 Emulation function on the "SB Live!" is working on the MS-DOS prompt on Win98.
Since I could not clarify whether VT8251 is support SB16 Emulation after reading of all articles on VOGONS.

P5VDC-MX has chipsets VIA P4M800 PRO+ VIA VT8251. I just installed "SB Live" into this mobo and then installed the driver (VXD version) on real Win98 session.
In conclusion, I could confirm this ENV could play sounds on several Arcade/Console platform emulators released for "DOS".

MAME (Multi-Arcade emulator)
Callus ( Capcom CPS1..)
ZSNES (Snes..)
Nesticle (NES..)
Genecyst (Genesis)

After that, I've also installed IO-DATA IF-SEGA/PCI. Still no problem.
In addition, UnichromeIGP on P4M800 is supporting VESA3.0 VBE function so this is works very well with those emulators.
So I've also add this mobo which is using VT8251 into the spare parts list for building retro console and arcade games.