You need to understand that products are designed to match the market. The two channel market has largely vanished except for the high-end, so there is very little product in the mid-range at all, much less something that would accept a digital input. There are a few $500-range amps and receivers, but digital interconnect is not usually there. By contrast, the AVR market is huge, and requires HDMI to even work at all. Once they're doing digital processing, optical and coax interconnect is easy and so finding an optical input on those things is fairly easy to do. Even a $250 AVR from Denon has an optical and coaxial digital input. It's the AVR-1312, on sale on the Denon site for $179, one optical input. So the $1000+ AVR suggestions are nice, but if you can't do that there are a lot of items across many brands that handle optical in the $250+ range.
Seems a little silly to just ask what they are here, when all we're going to do is look at the specs on manufacturers we sites.
You may now google at will.
