sunny Me again!
A voodoo 2
could be linked to your card. Problem is - V2's aren't made anymore. You'd have to get one second hand.
Performance wise, a V3 is basically two V2's slapped together - but on one chip / card. It's not quite that simple, but it's close enough.
It's also worth noting that you can install two Voodoo2's at once. That means twice as many slots taken up on your motherboard. Twice as much hunting around for second hand cards. etc. etc.
Also: Voodoo2's will still rely on the SiS card to some extent. That's not exactly ideal.
In short: The V3 is considerably more powerful, has that twin texturing thing - all sorts. It's the way to go.
Anyway, why do you want to keep the SiS card? The Voodoo 3 will replace it outright. That is; remove SiS card. Install Voodoo3. Done!
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P3 750 @ 750!?, 128MB of PC-150 SDRAM, Aopen AX63 Pro, V3 2000 @ 175, 13.6GB - 7200rpm WD Expert, SB Live Value, LG 40x CDROM, Jazz 300W Front Speakers + Sony SRS PC300D Rear Speakers / Sub Woofer, Sony CPDE200 17" Monitor, Full Tower Case, Win98 Original Edition.