I know the Thon Opera (due to its location at the Main Station and across from the Opera House). It's good; however, as Thon lists it within their "Conference' level, it won't be the least expensive.
FT member
Fornebufox mentions the Thon Astoria in post #7 of this previous thread:
http://www.flyertalk.com/forum/scand...l-station.html