The Ique should hook up fine to the performer. I think you have to take off the one touch ash system for it to work but it should work. I'm very happy with my Ique on my WSM. If you really think you're going to make a lot of BBQ you should start searching craigslist for used WSM's. Otherwise there are plenty of people who've made good Que on the Performers.
18.5" WSM / Weber Performer / Weber Genesis S-320 / Weber Genesis S-310 / 22.5" WSM