Streamers stream music from the cloud and offer digital connections (USB) to pair with a DAC. Unless you buy a digital player that has both which many do. So to be clear I think what you need is a Streamer/DAC with a volume control to replace the old SAE preamp. If it has analog outputs then it has a built in DAC. I really like the products that Aurender and Auralic make but they are pricey. If you want to just check out this whole streaming DAC business you could buy a Bluesound Node 2i (streamer/dac $600) and run it through one of your inputs on the SAE preamp. MIDFI?? is a tough price point for digital it seems like you go Bluesound or you have to spend $3000 to $5000 for a top end Aurender/ Auralic combo. Its possible that Schitt might make a product in that $1500-$2000 range. Happy hunting.
Matt M
Matt M