I also own many slow cookers and I totally agree with /u/cliffzig. the 6 quart is the one I most often use and timer attachment are not a good idea. Attachments won't set the cooker from "high" to "keep warm" after 4 hours and 30 minutes!

The first cooker we bought (years ago) was the crock-pot scv655. We changed it a week later for a programmable model (this one).