Austria to Italy by car - best route
 

My wife and I are taking a trip to Italy next May, and we decided to see a little of Austria on the way. We land in Vienna on May 8; We want to depart Vienna by car to the Austria/Italy border(3 days, 3 nights), then train to Venice. I am looking at the following routes out of Vienna;
1)Krems-Melk-Salzburg-Grossglaken Rd-Villach
2) Krems-Melk-Graz-Klagenfurt
3) Krems-Melk-Salzburg-Ischi-Klagenfurt.

Your thoughts on the best route would be appreciated.

Also, on the internet Klagenfurt looks like a much better stop than Villach for sightseeing, but Villach looks like it might be better stop to catch a train to Venice? What do you think?

Lastly, where would be the best location to pick up a car and stay away from Vienna traffic issues?

Thanks in advance for your help.

Just a couple of thoughts:

You won't see as many mountains on the Graz route as the Salzburg routes.

I found Klagenfurt more interesting than Villach.

~Liz

How about:

Krems-Melk-Hallstatt(optional)-Salzburg-Innsbruck

Train Innsbruck to Venice

I suppose you know that there is only 1 daily train between Villach and Venice (except 2 trains which stop at Villach in the middle of the night).
If you want to do the Grossglockner road (if it's already open in early May), try to drop off your car at Lienz in Osttirol and to go on by train to Toblach, then by bus via Cortina d'Ampezzo to Calalzo and by train to Venice. This itinerary is much more scenic and trains and buses are more frequent there.

Do Krems-Melk as a day's outing from Vienna and concentrate on sights farther afield on your way to Italy.