I'm using a MAG256 having previously used a MAG254 and it is noticeably faster. Generally reliable although it does crash from time to time. I've no experience with the 322. Check that your chosen IPTV service does support it. Not all services support all boxes.
If it is possible I would put the router close to the TV and connect from the router to the MAG box with an Ethernet cable. I was using WiFi and kept getting pauses but with a hard wired connection it is almost faultless.
Cosmote own all the telephone infrastructure, i.e. like BT in the UK, so providers like Wind are piggybacking on Cosmote. Personally I prefer to go directly to the organ grinder rather than the monkey. I have no experience of Wind but for people without a telephone line I believe they do some good deals on routers that use mobile technology, i.e. G4. I am told by a friend that their "Q" PAYG package is good value for money.