@wellsy37 

The entire network would set to the speed of the slowest device so everything would run as if they were AV1000 units.

Having additional units should help with the signal. With powerline, it really comes down to actually testing to know for sure, but you should get some improvement at the very least. This can be having all four active or just the 9020s. If you are going to have all four plugged in, make one of the 9020s wired to the router.

@Tony 

So then to add the two extra nodes should I not spend the extra $50 and just get two more AV1000 as it is the same performance?

@wellsy37 

Correct.