Hi Chris. I have a Stainz with a Zimo decoder and a Dietz sound card linked via a Suzi interface.
I didn't install myself, Peyker Modellbahn in Austria offer various Stainz models with fitted sound including a Massoth version too.
You can buy them form his Ebay shop.
My Stainz can be seen and heard here............
Excellent Austrian narrow gauge in North Wales.