WITH Mercedes-Benz and BMW busy creating cars that nobody even thought of – let alone asked for – such as the CLS, R-Class, X6 and 5 Series GT, we believed that Audi was going to keep out of the niche frenzy that seems to be enveloping the German car companies.

Yeah, right!

Suddenly there’s a four-seater five-door A5 for coupe buyers who wouldn’t dream of buying a sedan or a hatch. Tomorrow the conceptually similar but larger A7 Sportback lobs in, and the next-gen A3 is expected to splinter into a cavalcade of hatch, sedan and cabrio combinations to reach down into those market parts that no other premium car-makers can.

And these are just the niche models we know about. We’re half expecting an Audi aimed only at wealthy air-conditioner industrialists who long for a life by the sea but suffer from motion sickness, to be called the A-C6.

Right now, though, we have a stretched A5 Coupe with two extra side doors and a great one out back, using mostly A4 mechanicals and positioned between the A3 and A6. Just don’t call it an A4 hatch – that sounds so below Audi.

And why should it? That sloping rear roof line and small doors with no window frames might make getting in and out a bit more difficult than usual, but they look racy.

Once you’re ensconced in your comfy seats the beautifully designed and finished fascia from the A5 Coupe and Cabrio meets you.

In this regard there are no real differences between the models, and that’s a good thing because all that painstaking design and detailing is present, to give the Sportback’s occupants an uplifting experience.

But look behind you and the six-light window turret and rear bench seat (instead of separate bucket seats) make this A5 seem more A4 sedan-like than Audi would like us to mention.

If you’re about average height for an Australian male you might find getting to the rear a tad restrictive, but there is probably more headroom than you might have hoped for and less claustrophobia than you might have expected. Result!

Too bad Audi hasn’t catered the back-seat peeps with cupholders, however and why don’t the windows go all the way down like they should on a coupe? At least here are a set of air vents and overhead grab handles to hang on to.

And being a coupe with a large rear opening and a relatively low loading lip, you will have no problem laying midsized flat pack furniture back there, especially as the rear seats have a 2:1 split/fold function.

On the move we were about half impressed with the A5 Sportback’s driveability.

The entry-level 2.0TFSI quattro – likely to scoop up to 70 per cent of all sales – is a beauty, thanks to a sweet and willing turbo petrol engine that sings to the red line, pulls like a locomotive, and still manages to return less than 10L/100km. Married to the S-tronic dual-clutch gearbox, it provides instant and seamless performance on the agreeable country roads we sampled this car on.

Press on through mountain bends and our test car – wearing optional 18-inch wheels it must be said – carved up the roads with unfussed elan, sweeping up and down the snaking bitumen like it was born to be there.

On rougher roads, however, the ride deteriorated markedly, sending shocks through to the cabin and upsetting the hitherto premium travelling experience. Many of Australia’s rural surfaces also have a way of making themselves known inside via an incessant drone.

But this is small fry compared to the disappointing jerkiness experienced piloting the otherwise feisty 3.0 TDI diesel version.

Armed with an S-tronic transmission that jolted off the line as if a Shivering Scooby Doo was at the wheel, the flagship A5 Sportback (for now) was not a smooth drive.

Yes, with massive torque reserves to draw upon and an unassuming diesel working away quietly ahead of you, the 3.0 TDI’s straight line performance was outstanding, but the jolty lag that seemed to rear its ugly head after every acceleration attempt really made this car tiresome to drive.

Adding to the malaise was dull steering and a nose-heavy feel when driven through faster turns, while the ride quality seemed worse than it did on the smaller engine car.

In the end, we wondered why anybody would choose the A5 Sportback when the A4 sedan and Avant, as well as the A5 Coupe and Cabrio, all look better.

The first two are cheaper and offer more practicality, while the latter are sexier and better to drive.

Choosing the 2.0TFSI quattro and swapping the optional 18-inch wheels for Audi’s electronic damper technology would certainly help address the patchy ride quality issue and leave you with the lovelier drivetrain option, but the A5 Sportback is not the sort of compelling proposition that some other niche Audis have been over the years.

Here’s a new thought.

Maybe the company should concentrate more on making its core range even better and leave the model diversification to those who have already sorted out their cars dynamically.