So I've received my TVIP S-410 and I can only recommend it. It's very fast has great settings, huge buffer size. It supports both m3u-link and portal (MAC-adress). It can even record live-tv! Right now I am watching a hockey match in full HD without buffering which normally doesn't work at this...
I've heard that the best box for IPTV is TVIP S-410. They are much better than the MAG boxes apparently. People with buffering problems changed to this box and every problem disappeared. So I just ordered one, will let you know how it works.