I would argue going with an 808/818 is essential to get the most out of the speakers, but if it comes down to timing, get the best speakers you can, then upgrade to the processor.
This was my approach, but I had no idea what I was missing.
It's quite an old device, in terms of technology. It doesn't have Asynchronous USB on the input (the only M device that now doesn't), and whether it will be in any way MQA-compatible is an unknown.
While it fits perfectly in some situations I wouldn't buy one. It's bound to be replaced soon.