Ok I will ask the stupid question of the day, but what is the difference between the Calais - Berlina and Commodore? They all have pretty much the same engine selections and wheel base. I also think that most people would not be able to tell the difference by just looking at them. Can one of you Holden experts enlighten me?

My quick guess is that it's a similar to the Tempest - Le Mans - GTO were for Pontiac in the 60s.

Almost. Berlina, Lumina, Omega, Calais etc. are all Commodores—these are just the trim designations. Calais is the highest rung with more distinctive features—almost a seperate model, but not quite. Unlike numerous GM products from the '60s and '70s the different grades have not made the transition to an independant model life. Note that a couple of these levels (the limted value-edition Lumina and the standard Omega) are taken from export models—the Chevrolet Lumina sent to Asian markets and the Chevrolet Omega sent to Brasil.