Backpack for a Eurotrip

Hey guys,

I'm planning a nice 3 week trip, backpacking across Europe.

I'm in need of a nice backback to lug my stuff around, as I don't fancy dragging a suitcase all over the place.

The main things I'm looking for in the ideal backpack are :

1- Good quality

2- Roomy (At least 40-45 L)

3- Price (not looking for anything above AUD $200)

All suggestions are welcome :D