It didn't seem THAT bad. Our most recent rental was Peugeot 5008, which was pretty large, and we did alright.
We're going to have two cars, though. One larger, nicer car and a second smaller hatch. We need four doors, though.
when you ask "too large to handle in a city" what exactly are you doing in that city ? street parking close to shopping areas is either very expensive or prohibited in most large cities these days, and free spots are often extremely rare.
Parking in a parking garage is less of an issue (apart from really busy days), just prepare to move backward and forward a lot if you drive something with wide tires as most garages and parking spots will be rather tight
In general something like an A6 is no issue if you live in the suburbs and park in a parking garage when you visit a city, but if you're actually living in the city center you might end up parking a long way from home ... (assuming you have no private parking spot)
but then again like Onkel said even with a Golf you'll have that issue, and if a 5008 was OK I don't think an A6 would be problematic
Also, parking on the streets in French city centers = scratches & dents everywhere eventually parking bumper to bumper is the norm and to leave your spot you just ... well ... bump the rest out of the way. Saw a beautiful CLS in Strasbourg some weeks ago that could have only left its spot without scratches if its wheels would be able to turn 90 degrees sideways :'(