The reason that box is likely so cheap is it is using older technology. There is very little information since this is a uncommon brand name for these device. From their web site it says it is moca 2.0. That means it will run at either 400 or 800.
Although I think you had to have 2.1 to get the bonded 800 speed, I don't remember.
The newest units are using moca 2.5 which can easily get full gigabit speeds.
It is likely the units will work just fine. There is no real firmware you need for them. The chips that do all the work are likely made by the same companies that make them for all brands. Almost no end companies make their own chip, motorola used to but when the sold the moca business to arris I think they now all use broadcom or something.
Mostly the problem with off name brands is going to be warranty service, on moca stuff you don't need to worry about software updates because I don't think you can update any units.