Of course AMG now offers fast families the best of both worlds, with an all-wheel drive E-Class wagon that can also play the tyre smoking hooligan if required. In fact the similarities to the RS6 are uncanny, further proof if it was required that the Audi is the car to beat: both have twin-turbo 4.0-litre V8s, both have more than 600hp and both allow the driver almost infinite configuration to deliver their perfect uber wagon. Place your bets...
The day begins in the E63, because Nic really likes an RS6 and isn't someone to upset before 10am. No bother, because the Mercedes is excellent. Better perhaps than the saloon we drove recently, and not simply due to the practicality perks. It might be a placebo, but the ride of this estate - one of the chief bugbears of the saloon - does feel fractionally less punishing. It's still tough, it's still a bit irksome sometimes, yet here it doesn't seem to get in the way as much as before. Could it be the optional ceramic brakes taking a tad off the unsprung weight?
Then the Audi arrives with Nic at the wheel, broad shouldered, angry and intimidating. The RS6 also looks fantastic. There's a level of menace and a presence with the Audi that neither the passage of time nor the Mercedes parked next to it can diminish. Uberholt prestige may have little relevance in the UK, though we can be grateful that it has created such a cool estate.
'Charismatic' is a word that comes up a lot when discussing the big, fast Audi. Not only is that a phrase seldom used to describe a product with four rings on its grille, it's often a euphemistic term applied to cars with lots of power and little else going for them.
It rides with decent suppleness, controls its weight well and the sport differential makes the big old lump more neutral than you might expect on corner exit. Furthermore, older engine or not, this RS6 is still tremendously rapid. And it sounds better; sounds brilliant, in fact.
That the Mercedes raises the bar yet again is not a criticism of the Audi, more a reflection of where AMG has moved the goalposts to. The red car reveals weaknesses in the blue one you simply hadn't recognised before: a slight mushiness to the throttle response, the tiniest delay in gearshifts, occasional lapses in body control. By any other measure the Audi is great in these areas, and it's only this test that has brought those deficiencies - and even that seems too harsh a term - to light.
There's a distinct Nissan GT-R vibe to the way the E63 drives, and that's meant entirely as a compliment. Even if it does begin with the graunching and grinding of diffs at parking speed. There's that unrelenting and underlying firmness, yes, but also this sense of ceaseless twin-turbocharged speed and unflappable composure. There's traction, control and poise that you wouldn't have believed possible in something this large, and a balance to the 4WD system that enhances rather than detracts from the experience. After that, the Audi starts to feel a tad laboured.
Comparing a car that's been on sale since 2013 with a brand new one launched this year will always prompt calls of foul play, but when a rival is such a perfect fit the comparison has to be done. That the RS6 still comes out of this test with its credibility intact shows what an accomplished, likeable car it remains; declaring it the loser in this test seems deeply unfair, and even second seems to sell its achievements short.
In the company of this Mercedes though, that's how the result must read. It's an unequivocal victory for the E63, and it was never in much doubt. It's an astoundingly complete car, offering an armoury of talents with which even an RS6 can't meaningfully contend. This is one of the best AMG products ever, the engine tweaks delivering a level of excitement over a C63 and the interior a sense of opulence not that far off an S-Class. Previously that would have been sufficient for a deeply endearing fast Mercedes; that the E63 now also offers a formidably strong dynamic repertoire secures its place as the best super estate around, and confirms AMG is in a richly exciting vain of form.
SPECIFICATION - MERCEDES-AMG E63 S 4MATIC +
Engine: 3,982cc, twin-turbocharged V8
Transmission: 9-speed automatic, all-wheel drive
Power (hp): 612@5,750rpm
Torque (lb ft): 627@2,500-4,500rpm
Top speed: 186mph (limited)
Price: £90,490 (£108,835 as tested comprised of £2,595 for premium package including Keyless-go comfort package, Panoramic glass sunroof, Burmester surround sound and Multibeam LED intelligent light system, £295 for Air-balance package including interior fragrance dispenser, oxygen ionisation and improved filtering system, £6,995 for AMG high performance ceramic composite braking system, £765 for AMG Driver's package including an increase to the electronically limited top speed from 155 to 186mph and driver training from AMG's driving academy, £795 for AMG Night package including AMG body styling, radiator grille and mirror housings finished in high gloss black and privacy glass, £1,000 for AMG performance exhaust, £495 for 20-inch AMG five-twin-spoke alloy wheels in high gloss black, £295 for rear heated seats, £895 for designo hyacinth red metallic paint, £2,995 for AMG carbon fibre trim, £825 for Head-up display and £395 for 360-degree camera)
AUDI RS6 PERFORMANCE
Engine: 3,993cc, V8 turbocharged
Transmission: 8-speed tiptronic, Quattro all-wheel drive
Power (hp): 605@6,100-6,900rpm
Torque (lb ft): 516@1,750-6,000rpm (553@2,500-5,500rpm on overboost)
Top speed: 155mph (limited)
Weight: 1,950kg (EU unladen)
MPG: 29.4 (combined)
Price: £86,460 (£98,555 as tested comprised of £2,100 for Assistance pack, £750 for Audi hands-free boot opening system with advanced key, £250 for speed limit display, £810 for Parking pack, £6,300 for Bang & Olufsen advanced sound system, £630 for delivery charge including half a tank of fuel and number plates, £1,200 for road fund license and £55 for first registration fee)