I have 3 M4's currently. My home is quite big and although I have around 50 devices using the network, I think the issue I struggle with most is distance. The units vary between 20 and 30 feet apart and straight lines between the travel through several internal solid masonary walls.

I was looking at an extra unit and was wondering about the X20, but am thinking when used in conjunction with the M4's won't deliver much better performance than using another M4, am I correct or not.

If I were replace them all with X20's what differences would I notice in respect of distance between them (taking into account my solid walls.