I had one of the DXP4800 Plus NASes for about a month before RMAing it.
The CPU would immediately hit 100C with even the slightest whiff of load.
The entire thing was also unstable and would regularly just lock up without any kernel panic or other error message available, could even get kdump to gather anything (I'd binned their dodgy NAS OS and installed Debian).
It also seemed to amplify the noise of the hard drives within. Every thunk of a drive head moving around would be audible from a different room. Not sure how they managed to do that, but it's an acoustic nightmare.
Not gonna lie I dumped their packed-in OS like shipping foam. Turned the watchdog off, installed TrueNAS, not looking back.
I haven't paid attention to temps or noise - it's been suitable in my bedroom corner and it's been running for a month+ now like a trouper.