A little feedback for people wanting information about Vortex 2 cards.
I've been using an MX300 since it was released, 2048 Aureal betas since they were released, and never had any problems using the card or drivers with Win95 through Mill. Ed.
I've also installed both Win2k Server and WinXP Pro, and the card worked just as well in both OS'. I don't recall which drivers I used for Win2k, but as stated earlier in this thread, XP already had drivers available and installed them itself. Furthermore, either by some strange quirk or possibly built-in A3D support, I noted that in XP, sounds for things like menu pop-ups would correspond to the side of the monitor I had the cursor on (meaning, if i right-clicked on the left side of the monitor, the left speakers would deliver more of the audio than the right speakers, while clicking on the right side of the monitor delivered louder sounds from the right speakers. centered actions on the monitor seemed to deliver centered sounds). So the answer to "Do these cards work in 2k/XP?" is definitely "Yes."
To the question "Does A3D or A3D 2.0 work in 2k/XP?", I can't give an answer. To be honest, I never tested it, and I don't even use it now in 98. I have somewhat sensitive hearing (my co-workers thought i was nuts until the day i made all of them walk over and lean over to listen to the busy signal coming out of the phone that hadn't been properly settled in the cradle... which i heard from the opposite side of the room, over all the kitchen equipment i had running) and positional audio tends to be more disorienting than helpful to me.
I can also confirm that both audio output ports work in 2k/XP. I've been running a 4.2 system for some time (Altec Lansing ACS45.2 w/sub on front, ACS45 w/sub on rear), and all speakers were functioning in 2k/XP when I tested those OS'.
Good price if it's a Vortex 2 chip, and still better than onboard sound even if it's a Vortex 1 or Advantage. I'd jump on it, but I already bought 2 last time they popped up in a thread at this price (one for a friend, one for a future build).