What are the main differences between Audi A6 Quattro models?

I'm looking to buy an Audi A6 and I'm wondering what the main differences are between the various Quattro models. Can you provide some insight?

The main differences between Audi A6 Quattro models lie in the powertrain and performance. The A6 45 TFSI Quattro has a 2.0-liter 4-cylinder engine while the A6 55 TFSI Quattro has a 3.0-liter V6 engine. The higher power output of the V6 engine translates to a quicker 0-60 time and a higher top speed. However, if fuel efficiency is a priority, the 4-cylinder option may be a better choice.