Airport extreme

I currently use two power over mains adaptors to connect my netgear route and my airport extreme.

The netgear router in connected to my mac via ethernet cable. my extreme is connected via ethernet to my apple tv.

To extend my wireless network upstars i use an apple express which is wireless connected to the extreme.

This system works ok but i keep having messages on my mac to say that other devices are using varioue IP addresses.

If i were to use the extreme as my main router instead of the Netgear, could someone recomnend a suitable modem to use with it?.with my current system I very often have problems with loss of internet signal and e mail server and i am hoping that by cutting out the netgear router it will solve all the problems??

Thank you and regards

Bill