You'd be suprised. I've seen many 'entertainment' centers that have 16" wide shelves like Kicker has to deal with now. Even 'high end' AV stands, like StudioTech, are just barely wide enough (18").
Kicker, I personally don't know any receivers that are less wide than 17" but I know a lot of the digital switching receivers are both shorter and less deep than standard receivers so there is a chance something like that may fit the width requirement. There was a big to do about Panasonic digital receivers not too long ago (as in a lot of people were saying they sound great). Onkyo and HK dabbled in that segment too. Maybe investigate those options, you might get lucky.