Looks like they upgraded the processor and added some built-in connectivity for Chromecast and Apple.
I'm not really a believer in these pricey stand-alone streamers. The 658 is a little different because it can essentially serve as a preamp as well as a streamer if you need that (you also get Dirac room correction with it, which is a nice plus). Otherwise, I'm not convinced there is any audible difference between what you might hear from Tidal HiFi on the Cambridge vs the same signal on an AppleTV or Fire stick.
As for MQA, there is some debate as to whether it is actually higher fidelity than Tidal HiFi. I would not consider MQA support a must have on any streamer.