Getting around Europe is -way- easier by train. Eurrail passes are cheaper to buy from Australia through your travel agent than to buy once you're actually in Europe if you happen to know what dates you're going to be moving around. Avoid the "cheap" air flights at all costs if you have anything more than hand luggage.
You must at some point in your life hire an SL-55 or GT2 and go for a day of Autobahnning in any random direction in Germany. Schedule it in and take a spare pair of underwear, the boys and girls on there go past you at 260kmh smoking and talking on their phones while driving with their knees. It's a different experience. If you really want to test your driving ability, drive in Rome. Good luck, make sure you have insurance.
Major cities that I would consider must see's include:
Vienna (Austria)
Munich (Germany) - Home of BMW (100km away is Audi)
Berlin (Germany)
Prague (Czech)
Stuttgart (Germany) - Home of Porsche, Mercedes, etc
Salzburg (Austria)
Zurich (Swiss)
Paris (France)
Nice (France)
Barcelona (Spain)
Modena (Home of Ferrari, Lamborghini, Pagani if you look hard enough, Lancia, Fiat)
Milan (Fashion capital of the world)
Florence (Schedule in 3-4 days)
Rome
Venice
Asissi (If you or your partner are even vaguely christian?)
Budapest (Hungary)
Amsterdam, Brussels and Lyon are quite beautiful if you can be bothered. Also, many people talk highly of Zagreb in Croatia but I've never been there. Croatian beaches however are +++.
Tips: In Europe very little is "free". In many countries public toilets cost about 1 EUR. Beaches have entry fee's and almost all major highways are tolled except in Germany/Austria.
I only really included cities because I figured you'd be doing the obligatory skiing in the Swiss/Austrian Alps. (One of the worlds best ski resorts is on the border of Switzerland, Austria and Italy and is majestic.)
If you have any more specific questions, feel free to PM me mate. I've been to Europe well... enough times. My family still owns their family homes there and we don't rent them out because we use them enough