The first generation Avalon was based off the Toyota Camry, although it was stretched for a longer wheelbase. The only engine option was a 3.0 liter V6 making 192 horsepower. That engine was upgraded to make 200 horsepower in 1997. There was no manual transmission option for the Avalon, just a 4 speed automatic.
For the second generation, which started in 2000 and lasted until 2004, the Avalon was made larger, which followed the size increase on the Camry. The engine was given a slight boost to 210 horsepower. There were two trims on these cars: XL and the more upscale XLS. Interestingly enough, this Avalon was exported to Japan as the Toyota Pronard. It did not sell very well in Japan.
The third generation Avalon has been sold since 2005. Along with a major styling redesign, the engine received a major upgrade. The 3.5 liter V6 now makes 268 horsepower. The transmissions sold with this car include a 5 speed automatic and for the first time a 6 speed automatic. Sales have remained high in the United States, with nearly 90,000 Avalons sold in 2006.
There are more and more Avalons showing up on the used car market every day. Before buying a used Toyota Avalon from a local dealer, I'd check the bids on the various Avalons listed on eBay. They tend to be well below KBB.