The Malone Roof Rack, part # MPG201 is a confirmed fit for your 2003 Audi S4 Avant Wagon.
I've included our video review of it so you can get a feel for the installation process. view full answer...
Yes, The Thule Hull-A-Port Aero Kayak Carrier w/ Tie-Downs # TH849000 is compatible with the Rhino-Rack Vortex Aero Crossbars - Aluminum - Silver - 46" Long # RRVA118S-2 that you want to install on your 2011 Audi S4 naked roof. You will use the included T-slot hardware to attach the kayak carrier to the top tracks of the Rhino-Rack crossbars.
In addition to the crossbars listed above, you'll also need Legs # RRRLKVA and Fit Kit # DK208 to fit your vehicle.
Make sure you never exceed... view full answer...