Ethernet over Powerline - question about compatibility

I'm in the process of upgrading my ethernet over powerline setup, as I need to add two more rooms to the setup.

My existing arrangement is AV500, and it has worked well for about 4 years, with good stability and throughput. I ws going to add some more AV500 adapters (of a different brand, I can't get the ones I already have any more). Decent AV500 units seem to go for $120-130 a pair, with AC passthrough but only 100mbit ports. Av1200 units, with gigabit ports and 2-3 times the rated throughput over powerline, seem to go for around $170-180.

I figure that for an extra $50 the extra speed is worth it on my two main connections (ie the one attached to the router, and the one attached to the 8-port switch in the living room). My question is about compatibility. Say if I have:

Node 1: AV1200

Node 2: AV1200

Node 3: AV500

Node 4: AV500

Node 5: AV500

I understand that they are compatible, and that when the AV1200 talks to the Av500 the connection will be at the lower-rated speed of the two (ie the AV500's speed).

My question is whether having the AV500 in the mix, as part of the same powerline network, will have any impact on the speed at which the AV1200 units talk to each other?