The AC200 is not a Sooloos endpoint, so you need to feed it a signal from an endpoint. This could be an MS200 or similar, or via the USB port from a computer. The USB input as pointed out is synchronous and limited to a much lower resolution than that of the asynchronous input for the 818v3. Due to being synchronous it is potentially subject to a significantly higher level of jitter.

The 818v3 has a Sooloos ID41 card built into it, so for a Sooloos-based system this is much the best input to use. It also benefits from a Linear Power Supply and significantly greater processing power than available in the AC200. This enables triple FIFO buffering to reduce jitter to extremely low levels, as well as significantly greater interaction with your SE speakers than the AC200 can. This includes MQA decoding which the AC200 can't do.

I agree the 818v3 is a significant step up in price, but that's because sonically it can achieve a lot more than the AC200 (as I said previously, I view mine as a source switching device rather than something that inherently adds to the sound; this is a very simplistic view).

Only you can decide whether it's worth it but having gone from a 568.2mm to an 861v4 recently I'd say you may be surprised how much better things can get.

Sooloos, Roon, G series (with LPS upgrade), 800 series (with LPS upgrade), HD621, AC200, Prime and PS, DSPs old and new.

Purdeys, Moke, Leica, 'Blad. Only the best.