With a Vortex 2 card you only need swap to either using the 2.25 A3DAPI(A3D 2.0), or the 3.12 A3DAPI (A3D 3.0) to get most if not all A3D games working properly. The 3.12 A3DAPI does however require driver version 2048 or 2050 to work with A3DVerb which was their EAX 1.0 emulation.
Sensaura on the otherhand is DLL specific and for each A3D game you need to swap and mix DLL versions, I however experimented alot and found the best combination:
This seems to be the best Sensaura A3D dll combo for gaming. If you need A3D 3.0 games then just replace the A3DAPI.dll with the 3.12 version. but leave A3D.dll and Audio3d.dll at these versions.
A3D.dll is Audio3d.dll version 12.1.2009 (fixes Half-Life detection issues, so you no longer need the official Aureal version)
Audio3d.dll is version 12.1.2008 (Makes Chaotic WaveTracing work in all A3D 2/3.0 games)
A3DAPI.dll version 2.25 (Required by many A3D 2.0 games to work properly, version 3.12 works but is buggy)
Sensaura is a great audio engine, there was however only one game which was written just for Sensaura with the Game CODA middleware. Men of Valor (2004), it sounds pretty good but isn't a shining example of Sensaura features.
Sensaura will accelerate any DS3D and A3D games, with EAX 2.0 support. It supports piggy backing off the A3D 2.0 game geometry and replaces the WaveTracing with Chaotic WaveTracing, which sounds pretty awesome in Half-Life. Even though it wasn't stated as supporting A3D 2.0 it does support piggy backing off it.
I have the Santa Cruz and it works really well for every game I've thrown at it, however there are games which bug out and have clicking and/or missing samples. No soundcard is perfect in this regard while supporting all the major API's at the time.
Sensaura get high marks from me as it is a jack of all trades audio engine and does VERY well compared to the rest of the pack.
However there is no perfect equal to the A3D 2.0 engine and there were only a handful of games that implemented it well. So If you want A3D 1/2/3.0 support stick with the Vortex 2, if you want a Jack of all trades with great HRTF and some A3D/EAX features get any CS4630 based card, Santa Cruz, GameTheaterXP ect...
There is a good topic here that covered a lot of info