Yeah... I have a Perfoma 6115CD I added the DOS card... I have Win 3.0 and DOS (Not easy to use) but hay.... Its cool... My FIRST Ever Mac... And that lead to me having 250+ Macs now...
I still have a 6100, and I used to have that DOS compatibility card in it.
I did run Windows 3.1 on it, and was super at the time!
Later I put a Sonnettech G3 card in it, and got the AV card for it too. Therefore the DOS compatibility card had to go out (got a PC anyway). But I haven't used this Mac for some years now.... it is part of my little Apple museum now (you probably also know the feeling...I just can't get rid of any Mac).
As this was one of the first PowerMacs, I can justify never getting rid of it. Somehow you can find an excellent reason for all your Macs never to be disposed of (even the 4400, as this was the ugliest!)