London: Bringing glamour to the modest models on which they are based, they can bring a significant boost to sales across the brand.
The three main players need little introduction: the BWM M4, Mercedes AMG C63 and the new Audi RS5, which we have to test this week.
Talking about bestowing brand kudos, few have done this more successfully than the original Audi Quattro.
In the early 1980s the four wheel drive rally car set new standards for performance.
Forty years later the RS5 is its natural successor. Though you are much more likely to find in in the executive car park than a gravel stage.
The fabled all-wheel drive is still there of course, but its main use is to enable the full deployment of the 444bhp.
Despite a downsized engine from the previous generation, it plays a significant part in getting the RS5 to hit 62mph in less than four seconds.
And on a wet slippery roundabout in January you will be glad drive goes to all corners, with torque vectoring and drive splitting almost imperceptibly.
It is a devastatingly quick point-to-point machine which instills very high levels of confidence.
The downside of this is that it’s almost too easy. The sense of fun has been ironed out as it does going rapidly with such clinical ability.
But this is still a car that could out sprint a Ferrari F40 by almost a second and they both share an engine size of 2.9 litres.
Gone is the previous 4.2 litre V8, replaced with a smaller unit with two less cylinders.
Turbo charging means is still has the same power output, and the sprint time has dropped by half a second.
The slug of low down forced-induction torque is fed through the new 8-speed tiptronic gearbox. The resulting linear acceleration is almost Tesla-esque.
Unfortunately it also shares the acoustics of an electric car.
Despite the added optional £,1200 RS Sports exhaust and four howitzer sized tailpipes, the downsizing and turbo has robbed the RS5 of a lot of the aural pleasure.
Following an M4 into an underground car park, the rival’s rumblings left the Audi trailing meekly in its wake.
Granted things do liven up when you Sport is selected and you open the taps more and unleash the full anger of the engine.
But is is not as it was, maybe it’s the way things have become in the more silent digital age.
Not that there is anything quiet about its road presence.
The revised grill, bonnet bulge, vents, skirts, silver mirror caps and spoilers shout “move over, i’m coming through.”
Inside it is typical Audi fare, just turned up a notch further. You will struggle to find any car with a better interior cabin that does not cost six figures.
The quilted leather Nappa Super Sport massage seats and mechanism to offer up the seat belt is all very Bentley.
The light tactile clicks on the volume knob and padded alcantara door cards, are of the highest quality.
No one buys a saloon for load lugging but the boot is a very useful 465 litres. It is a fine motorway cruiser when it needs to be.
Rivals all keenly priced around the £60,000 mark. With a budget like that and when the first year car tax will be £1,200 then £450 annually, it comes down to personal preference.
Although the RS5’s technical ability and performance are additively outstanding, it does lack some of the drama and excitement of competitors.
It is similar to the German football team – while you can admire the relentless efficiency it is hard to love them.
The RS5 is a super saloon for the modern world – faster, quieter and easier to drive.
Whether that makes it better is a matter of personal taste.
Audi RS5 Coupe
Top speed: 155mph
Power: 444 bhp
Engine: Petrol 2.9l V6 turbo
Gearbox: 8 speed auto
Fuel: 32.5mph (combined)
Emissions: 197 g/km