What is the best site to purchase a train ticket for this trip?
Anyone?
Kelsey,
buy the tickets at the Austrian railways:
http://www.oebb.at/pv/en/index.jsp
make sure you go with the SC (Supercity), the tickets cost only €29. You will arrive at Wien Südbahnhof.
The trip takes a little over 4 hrs and it's a direct connection.
Happy travels