As a report, I can say that my Grandstream HT814 has been a great product. I did not have too much trouble, and got a little tech support to configure it. Once you do it, you would have no trouble at all.

It is compatible with VOIPO, and has worked seamlessly since proper configuration. It also gives more options for fine tuning.

It was easy to configure each port as desired. The configuration I used was two ports paired together in a two-and-two setup to give me exactly what I wanted.

I strongly suggest that VOIPO support these products directly. They should also be given out to everyone with two lines. It saves a lot of unnecessary space, cabling and configuration.

Next, I am going to a free PBX package on a Raspberry PI with a PoE router and cordless IP phones, which should be a lot of fun.