I buy classical SACDs from Amazon, Presto, Berkshire Record Outlet, and eBay.
Kal Rubinson , who has posted on this site, has reviewed a few multi channel DACs. As has been mentioned, none of these are by mainstream companies. They will all be costly. So if having a multi channel DAC is a priority, I would go with a processor-pre amp combo. McIntosh would be my choice. Alternatively use the DACs in the player.
One could get a 2 channel DAC for the fronts and then use the processor or receiver DAC for the center and rears. The fronts are going to handle the bulk of the music in a good (non gimmicky) SACD, with the rear being for ambience. I actually did this for a while using an old DAC and and Anthem 5.1.

