I'd look at the Denon X3800H instead of the 70s. It will give you full XT32 out of the box with the ability to upgrade to Dirac Live. If you're in love with the Marantz aesthetic, you'll need to go to the Cinema 50, which is the X3800H's twin. The 3800 is $1500 on Amazon right now, though it has been known to go on sale periodically.
MQX is great. Is it worth $200 compared to a Dirac Live license, though, particularly given the upgrade path to DLBC and ART? Up to you. Yes you can import from REW using MQX (again, $200 license for that feature), but I think it would be rather complex to average a multi-point measurement in REW to do what Audyssey and Dirac do at the press of a button. The better use-case I find for REW is to measure the result post-calibration and make adjustments as necessary.
Regarding the Eversolo, it's a 2-channel streaming integrated amp with the convenience of an ARC input. It's largely meant for dedicated 2-channel music listening. You can use it with ARC, but it's worth noting that the Eversolo cannot decode many codecs used by TV and film content. At best, it might be able to decode old-school Dolby Digital, but I don't see any logos on their site, so that's not guaranteed. This means that if you're bitstreaming these codecs (Dolby, DTS, Atmos), you'll get nothing but silence. In order to use something like the Eversolo in a home theatre context, you need your TV (or upstream source) to decode to PCM. The problem is you don't have much (any) control over that process. Does it downmix 5.1 and 7.1 into stereo PCM? Does it just drop all the channels except FR and FL and send you those? Depends.
The Eversolo also lacks room correction entirely. If you're using it exclusively for 2-channel streaming using Roon, then you can use Roon's convolution filter to do your RC and you're good to go. But that won't work with analog sources (or ARC) and....the Eversolo is not Roon Ready yet. If you want Roon and Room Correction, but still want to run a small integrated amp instead of an AVR, then you could look into an NAD M10 V2. That would give you Dirac Live, Roon Ready, and Dolby Digital decoding, plus multi-room streaming support. Long story short, I think the Eversolo is a bad idea all the way around and to be honest, their lunch is going to be eaten by the Wiim Amp at the low-end given their (Eversolo's) price point and lack of features. At the high-end of the admittedly tiny integrated market, you have the NAD M33, Hegel H600, Naim, and too many more to list.