Most people won't have the money to buy an RS6, because with a starting price of around \u00a377,000 it could hardly be described as a mass-market car. But there are plenty of people around who do have the money, and are looking for a high-performance car with some practical skills too. It's perhaps the combination of power and practicality that really attracts us to this car so much. And it's remarkable how far estate cars have come. Once seen as boring vehicles\u00a0bought by people who needed to haul bulky wares around the country, the estate didn't start to get interesting until the likes of Volvo, BMW and Audi turned up and turned them into elongated powerhouses. With the RS6, we have to say, Audi has won our hearts with the design. Look at the front, with its super-aggressive headlight design and that massive open mouth. These all go brilliantly with the bi-turbo V8 mounted under the bonnet. It looks like it's shouting at you, and when you stand on the accelerator, it sounds like it too.The grille on the model we drive is one possible option, but you can also go for a split grille that divides the intake just below the number plate. With this option, you get the "quattro" branding stamped in massive letters across the front. It's a bit ostentatious, but from a design perspective it's a brilliant, bold choice that we really like. There are loads of customisation options too, like having carbon fibre trim and a front splitter that give the car a proper sporty style that\u00a0you'd expect on a Lamborghini.The engine deserves some specific discussion too. It's a 4-litre V8 with two centrally mounted turbochargers that can produce 560hp and a top speed of a touch under 190mph in the highest spec car. It also gets to 62mph in 3.9 seconds. That's not quick for an estate, it's quick for a two-seater sports car, in fact it's the same speed as the Porsche Carrera S and three seconds faster than the plain Carrera. Technically, this car is less powerful than the one that went before it, but massive weight savings - 100Kg we're told - mean that it's faster to 60 than the previous car.In spite of that somewhat amazing power output, Audi has also done a lot of work making this car as economic as possible. According to official figures, you could get 28mpg out of this car if you drive it sensibly. It has Audi's cylinder on demand, so when you're doing 20 in town, it's not, as the expression goes "firing on all cylinders". Ignore the negative connotations of that expression though, here the Audi is ready to go flat out at a moment's notice, it's just not very wasteful when you're doing the school run.We got the opportunity to drive the RS6 on a sunny day just outside Munich, which was every bit as fun as it sounds. A blast down a German motorway is an event worthy of travelling for and the RS6 really is jaw-droppingly quick. Push your foot down, and the car will drop either one or two gears, and you're off with some ferocious acceleration. We got 240kph out of it, and it was nowhere near running out of steam. It is, however, worth pointing out that all the versions of the RS6 are limited to some extent.It's more than quick though, it's also a remarkable place to sit. Comfort is first class, with a driving position that feels like you could sit behind the wheel for days. We instantly fell in love with the head-up display. Here you get a display of the speed you're travelling, directions if you've got the sat nav turned on and indications of the speed limits on the current road. You're also warned here if you're getting too close to the car in front, with a red indicator that makes its point without being too much. This head-up display is really, really useful and it means that you never need to take your eyes off the road. If you're going quickly, that's a real boon to safety and on\u00a0de-restricted\u00a0German autobahns it's essential.So, it seems to us, if there was such a thing as the perfect car, the RS6 might just be it. You've got more space than any sports car on the market, and a boot that can take a week's worth of suitcases for a family of four and acceleration that can beat a Porsche 911. You've got ISOfix brackets behind you, and 560hp of V8 twin turbo engine in front. It's a car that makes almost no sense at all, but at the same time, it's a work of complete genius.So, if a sports car is impractical for your nuclear family, then the RS6 is the answer. There's no shortage of fun here, and no shortage of practicality.