Ewif you need long enough rcas, grab a pair of scoshe twisted cables... 25ft. for like 20 bucks i think? something like that
You might be able to use 6 ft RCAs if the amplifier is going under one of the front seats. Take a piece of rope and run it tightly along your planned layout to see how long the RCA needs to be. If you route the RCAs away from the usual sources of radiated noise(blower fan, fuel pump, relay packs, etc.) you don't even need shielded RCAs.I know shielded (and I think twisted ) are great to get, but don't know which ones to get that are actually good and also is 6 feet long enough for a Passat wagon?