Where have you been!
Do a forum search for Canton and my name and you will see tons of comments (along with many others)!
However, my quick & dirty summary is to try and get the models with the ceramic tweeter if your budget allows! Below that pricepoint I would generally reccomend other speakers like teh Infinity or JBL (when on discounted).
So, for the ceramic tweeter, we are talking Chrono SL 5X6.2 (where the number in the "X" position will distinguish between the size and type (tower, center, etc).
Any of the Ventos (which are a level up from the Chrono SL) have the ceramic tweeter unless they are one of the older models (A4L still has a few to sell). Just check the spec to make sure "ceramic" is in the discription
I have not heard any Canton above the Vento. My understanding is the Vento Reference have nicer drivers and I have to believe they are better, but I have not experienced the Vento Reference.
If you are interested in a pair of bookshelf speakers for surrounds for $650, this is a very good deal:
www.accessories4less.com