The Achieva started out with 4 trim levels. They were the S, SC, SL, and SCX, ordered by priced. The SCX was the highest performance model.
The Achieva was sold standard with an I4 engine, but some models got the more powerful V6 engine. The SCX, however, got a smaller I4. That I4 just happened to be the most powerful NA I4 engine ever made by General Motors. It was a Quad 4 I4 called the W41. The Getrag 5 speed manual transmission was specially built for these engines.
Following 1995, the trims were trimmed down to just two options: the Series 1 and Series 2. Both were available as an S coupe or a S sedan.
These are not bad cars, and the Achieva lived up to its name by outperforming most compact cars of its time. If you are looking to buy a used Achieva, and by now all of them should be well used, the best place to look is on eBay, where you can also find some good deals on parts.