DAC's and other Interfaces

Hi all.

While I wait for the Stas’ Update to allow my iPhone App to function, I’m pondering other aspects, like how I will hook my existing audio equipment into the AC650.

Background: I’d been using a Fosi ZD3 DAC as an Interface for my TV, mostly because it had a HDMI connection on it, but also the TV is basically a Streamer too with Spotify etc. This DAC then too acted as a PreAmp which fed a Signal to 2-V3 Fosi Mono Block Amps.

My intention is to use the V3 Mono’s to Power my Bass Section on my diy 3-Ways via RCA Channels 9/10. That’s straight forward enough. My Real Question though is how do I utilize the the ZD3 DAC, or do I even Need to?? I mean, I can grab the Optical Audio Signal from the TV, then go right into the AC650, but does it need DAC processing making the DAC redundant??

IF I tried using the Fosi ZD3 I would be limited to RCA Out via 2 Channels, but then there is only a Single RCA Input on the AC650. Could I just use a RCA to USB Cable like this?:

Obviously I’m a little confused and outta my depth here and any/all help is greatly appreciated!

TIA Bob

Pic of Fosi ZD3