This S6 Avant is based on Audi's C4 platform. It's powered by a turbocharged 5 cylinder engine. 60 MPH comes in just over 6 seconds and its top speed is just under 150 MPH. Being an Audi, it's AWD.
This is one of those "tastefully modified" cars, meaning the mods are useful, but don't change the basic look or goodness of the car. It's been chipped and has a European 6 speed transmission. It also has European headlights with aftermarket HIDs. The windows have a 50% tint, which I'm not a fan of (and would be illegal in some states), but the rest of the body is stock. It appears to have been well maintained.
Located somewhere in CA, click here to see the eBay listing.
A big thanks to John for sending me the link to this car!