1. You don't need SACD for sound quality reasons. DSD64 - the format of SACDs - has frequency extension and noise performance that make it roughly equivalent to a hypothetical 56kHz, 20-bit PCM. Of course such a PCM format doesn't exist. But SACD's noise floor is about 20 bits, and its noise-shaping usually results in a huge amount of ultrasonic noise starting around 28-30kHz (a PCM sample rate that could go up to 28kHz would be a 56k sample-rate system). So don't bother with an HDMI de-embedder or anything like that. SACD does not sound different than PCM, and 24/48 PCM is more or less identical in capability to SACD - slightly better noise floor, slightly less ultrasonic frequency capability. But it doesn't matter, because we can't hear the difference between 20 vs 24 bits, and usable frequency response up to 24kHz vs 28kHz doesn't matter since we can't hear past 20kHz anyway.
2. You "need" SACD only for a relatively small number of specific masterings. There are a few masterings of some albums that have only appeared in SACD format. For example, the two 2003 Talk Talk SACDs used a then-new mastering on their SACD layers, but for the CD layers they re-used an existing 1997 mastering which IMHO doesn't sound as good. (Of course, each of those SACDs will cost you $100 or more on the used market, so why bother.) There's also a series of Universal Japan SACDs from 2009-2011 that are reputedly flat transfers from the original master tapes. These are single-layer discs - they don't have a CD layer at all. But many of these flat-transfer masterings have subsequently been released on hybrid SACDs and/or on plain old CDs - not to mention that not all of these particular masterings are the best-sounding ones out there anyway. I do find the 2010 Universal Japan SACD of the Who's
Who's Next to be the best-sounding version I've heard, and I don't think it's ever been reissued on a hybrid SACD or a CD. But there are multiple other very good versions available on CD.
3. The UBP-X800M2 is an excellent disc player for other reasons. In addition to its ability to play Blu-Ray and DVD-A discs, it's also the most
mechanically quiet player I've ever heard - or, I should say,
not heard.
I don't know what your preferences are or what the ambient room noise in your listening space is, but the X800 does not emit any of the little beeps or chirps that most CD and DVD/Blu-Ray players do periodically when playing discs, especially when moving from one track to the next. The X800 also shows nothing on its display when playing discs, because it was designed not to be distracting when hooked up as part of a home theater system. I personally love this even though it's in my audio-only setup, because I don't like the distraction of a bright LED display when I'm listening to music in a dimmed or darkened room.
Given that the 800M2 costs only about $250, and part of that cost is the heavy metal chassis that is responsible for the fact that none of the mechanical spinning and track-seeking noises escape the player where you might hear them, I view it as an excellent value, and so I would suggest you consider keeping it even if you go for a simple digital TOSLINK connection to the MiniDSP, which would prevent you from being able to play SACD layers through your system.
So my recommendation is to keep the 800M2, connect it directly to the Flex with a single TOSLINK or other digital cable, and don't worry about anything else.
