Seeing as I'm from the other side of the pond I may be able to help you out.
The top snow-sure resorts:
Hintertux
Karpun
Stubaier Gletscher
Zell am See
Those are all glaciers, then other places to definately check out are Schlamding, it's not a big resort but last year it opened up in November! Then another great place is Saalbach am Hinterglemm which has 3-4 different parks and a lot of terrain to cover. There is also places like Obertauren
Out of the resorts I've listed I've only been to saalbach and the stubaier gletchser, stubai isn't really park-orientated or backcountry for that matter, it's more of a family place..
One guy mentioned St. Anton, definately go there. The ski pass also covers a small nearby resort called Sonnenkopf am Arlberg, it's a really small resort but with huge open bowls and some good tree skiing. I was lucky enough to be there in easter when it dumped overnight and bluebird by day. Some of the best powder I've skied.
Also, Vienna is quite a way from the Salzburger alps sadly, but you should check out the salzburg super ski pass which gives you access to 23 huuuge resorts and a net total of 2,200km.
http://www.salzburgsuperskicard.com/eng/index.html
Hope that helped!