I have two 1st gen Aztech cards with the Covox/DSS feature:
- NXPro. Definitely the most common out there. Does the job, but no WSS codec, so not what you want. Note that the NXPro 16 is a different card that does have a WSS codec, but supposedly no Covox support...
- MMSN810. Probably the most feature-rich sound card, so highly ironic it's referred to as "Sound Galaxy 16 Basic". SBPro2, real OPL3 (or 1:1 clone, Aztech used both) and WSS codec (either AD1848 or CS4248 depending on what was in the last rubbish bin Aztech raided)
Only downside is no MPU-401 MIDI. Aztech's 1st gen cards don't offer that.
Both work pretty identically software-wise (other than WSS or not), the NXPro is pretty system.bus noise-sensitive, similar to the original Sound Blaster. I have the feeling (but it's no more than that) that the MMSN810 is less sensitive, but haven't done any systematic measurements.
In terms of compatibility they're good, but not perfect. In general they do the job and also support ADPCM (only relevant for Duke Nukem 2, but a lot of people care about it), but I've not been able to get Ultima 7 to give me digital samples on either.
Personally I far prefer Aztech's 3rd gen cards (AZT2316x chip) for general builds as they are very quiet and have perfect bug-free MPU-401 MIDI. Pair one with a buggy SB16 and you have the perfect mid-1990s setup. These 1st gen cards are more interesting for early 1990s stuff, where the rough, noisy nature of the card is more of a feature than a bug. I intend to combine one with my SSI-2001 replica and a CMS clone once I decide which I want for a turn-of-the 1990s jack-of-all-trades.