I've been running AV Homeplug 200mb for a few years now and are considering upgrading to 500.. The problem is I have 5 of these units, and they are not cheap.. Is it possible to run the 200 and 500 units on the same cables? I presume they wont be able to talk to each other directly, but if I start by switching a couple of the units for 500 homeplugs (assuming the router will route the traffic between the 200 and 500 units) will they then work alongside each other?