The reason I want to upgrade is the Sonos does not support MQA.
It seems like you have read some articles from a few years ago. Ignore all that MQA garbage. That suggestion posted by soix above is a good one, and it is from a dealer- if you are truly looking for sound quality improvements it would be really hard to do better than that for the money, considering how much does 500 GB of music cost? It will be gone soon guaranteed.