Most of the Amazon stores are NOT authorized dealers, if you purchase from any of them you're not going to have a warranty.
Also there are some other black market dealers that have been using the names of authorized dealers on auction sites. Be sure that they are the real deal before you waste your $$$.
If you have a link to this Crutchfield deal, please PM me and I can check it out.
Here is one Ebay/Amazon dealer that recently got busted:
http://www.radarroy.com/archives/204