Have you tried a dummy HDMI dongle to trick the 5700 into thinking it is driving two monitors? Supposedly increases eGPU performance a lot. It is reckoned to be a driver issue.So in other words, I didn't have to buy a new eGPU enclosure. It was the fault of the OS. Great.
I like the Razer box a bit more because it's so easy to work on -- one handle opens the entire unit. It's a bit slimmer as well. But the Sonnet has more power, so I guess I'll keep that one for future-proofing (if that's even possible with current tech).