question about EMM

I want to try used EMM. Which model should I get? CDSA? CDSD? How do they compare to a computer audio as a transport?

CDSA is a one box player
CDSD is a transport alone.

You may want to look into a EMM labs MA-1, which is a DAC that will handle USB input and a transport.

The MA-2 is an MA-1 with a CD transport.

If your budget extends to the MA-1 or MA-2, also have a look at the Playback MPD-3 and MPS-3