Need advice in new setup

HiDoes anyone have some advice on what might be a sensible and reliable network set up:I have an old desktop that needs to be retired, and since I'm getting issues with wifi drop out I thought I would update the network at the same time.Currently:

On Vodafone cable in Kapiti and it uses the original Motorola Surfboard modem

This runs to a Belkin router F5D8236-4v1(01)

Also have a Netgear range extender in the lounge so I can connect AppleTV, Bluray and Receiver - all cabled

Normally connected via Wifi are Playstation, Ipod, IPhone, Windows Phone, two laptops and whatever guests happen to bring

I thought I would get a new Wifi router - should I replace the modem? - that I can connect to storage for music and photos, and just get a windows tablet (one of the laptops is a work one and I don't want to fight with my better half for the other one) to run Itunes so I can run Itunes and maintain the AppleTV - it's 1st Gen that has on board storage and has to sync to an instance of Itunes.Any advice on whether this is a good idea or not, and cost effective device recommendations would be gratefully accepted.Thanks!