For AE rendering purposes –
1. The more RAM one has, the more AE will use, with the remainder reserved for other applications as set by the user.
2. The AE render will use all the cores and threads the cpu has (even when multi-processing is turned off)
3. The faster the cpu speed, the faster the render.
So, in choosing a rendering machine, it is a balance of more cores and threads versus cpu speed. The Xeons are generally slower than the mainstream processors (eg. i7 6950X, i7 6900K, etc) when compared unit against unit. But the Xeons have more cores and threads which AE will use in a render, and if one doubles that up (dual Xeons), I dare say that rendering will be much faster despite each Xeon having a slower base clock versus the mainstream cpu.
The BOXX Rendering machine seems solid for the purpose. Suggest you contact them for your requirements (for AE not 3D rendering) and see what their reply is. Granted there appears to be no reviews to date, but generally professional users seldom revert especially if there are no problems with the unit(s). And being a specialist market, the mainstream media would rarely, if ever, be provided a unit for review.
For a read/research, here is a build your own for a modest price –
https://www.techspot.com/review/1218-affordable-40-thread-xeon-monster-pc/
…with a more modest unit in an earlier article –
https://www.techspot.com/review/1155-affordable-dual-xeon-pc/
good luck!
Thomas Leong