But the PC/DOS version does not?!

https://www.youtube.com/watch?v=7Fm3zZClHsU

Please tell me there is someway, like a mod or something, that incorporates The SEGA CD voices within the base game?

Not likely, unless someone decides to do a full remake like The Ur-Quan Masters for Star Control 2 which can incorporate the 3DO voices.

The 3DO and Mac versions were actually the definitive versions of the first game:

https://www.youtube.com/watch?v=CFTdhyKhq4g
https://www.youtube.com/watch?v=gqN_A_bHBNw

As one of the lucky few to own the Mac version and have it running perfectly on an old beige G3 i'll say this.

Considering the sheer number of changes to script and story, as well as everything else about the game. I would characterize it as a different game entirely from the Dos games. Not the "definitive" version.