Train travel in Europe is dirt cheap compared with Australia.
As with any worthwhile decision in life - do plenty of research before you push the button!
In Germany for example the DBahn has regular sales with fares to/from Germany to other countries as low as 19 Euros with the trains (for the bulk of the journey) be the 180+km/hour rockets for example.
Eurail passes can be good for some but it really does depend. For our family, they would have been a waste of money. For others they're great and people use them as a free 'hotel' - taking an over night trip so they don't pay for a hotel.
As for business class on the airlines - Singapore Airlines,
Etihad both will earn you Velocity Frequent Flyer points, while the Oneworld airlines will earn you Qantas points. So perhaps its time to join Velocity frequent Flyer (if you have not already). Many AFFers have multiple frequent flyer accounts across airlines - gives you a wider choice and often better seat availability when looking to redeem some of your points for flights.
For example First or Business class to Europe on Singapore Airlines can be purchased by transferring Velocity FF points to your soon-to-exist Singapore Airlines program account (called KrisFlyer).
So many options and so much fun gaming them!