M6 duo low and large

BMW M6 Photo / Supplied

Latest 6-series doesn't disappoint - but you might need a Lotto win

BMW has generally played a fairly safe design game when it comes to its highly-rated M range.

Over the M Sport skunkworks' 40-year history, there have only been a handful of machines that have really pushed the boundaries in terms of looks. They've been sensibly German with a whole lot of fire-power tucked away underneath sedate-looking shells.

And seemingly anyone who buys a keyring or pair of M socks gets a badge to slap on the back of their car - whether it's a racebred M monster or a softly-softly 318i - so from a distance, it can be hard to tell what's an M and what is merely wearing its hat.

But the 6-series is different, and has been since the stunning M635CSi all those years ago.

The latest big coupe and convertible combohas launched to give a serious, and seriously expensive, alternative those not wanting to take a step further than the executive-in-a-hurry look of the M5.

Mechanically, the M6 packs the same 4.4-litre twin-turbo V8, belting out 412kW and 680Nm of torque.

The current arms race between the German manufacturers is serving up some serious weaponry to those who are looking at cars commanding a cool quarter-ish million.

BMW can hold its head high here, with both the coupe and convertible exhibiting huge road presence - low, long and large with very aggressive wide front spoilers all sitting atop big, flashy wheels. It looks fast even when it's stopped.

But it isn't just the opulent looks that M6 buyers want - it's the packs of equipment that can be expected in a car that carries a price tag that leave most wondering if they should buy a Lotto ticket today.

A full safety kit is included, with lane departure warning, park distance control, a million airbags, a HUD (head-up display, which projects speed and other information so it seems to float halfway down the bonnet), even internet connectivity and BMW's nicely-rendered new 3D sat-nav. In the coupe there's a 16-speaker stereo to enjoy in your body-hugging leather race seats, and in the convertible there's 12.

There's also engine stop/start, if you're concerned that you mightn't be doing enough for the planet with your twin-turbo eight-cylinder engine. That said, considering the incendiary nature of the engine package, it's combined thirst figure is rated at 9.9L/100km for the coupe and 10.3 for the soft-top.

Carbon output is 232g/km and 239g/km for the two respectively.

This dynamic duo tips the scales in the neighbourhood of 1850-1980kg, depending on model, and can still hit the legal limit in just 4.2s (or 4.3) and onto an electronically limited top speed of 250km/h.

Good numbers indeed, and during a test session at Lakeside Raceway near Brisbane, blasting past the 200km/h mark wasn't hard - a stomp on the right pedal and hooking the steering wheel mounted shifters every time the robotic seven-speed gearbox was about to hit redline, and even on a short straight we were easily into the danger zone.

An easy couple of million dollars worth of M6s left central Brisbane on the way to Lakeside via a couple of challenging mountain roads - one which supplied an incredibly steep grade with seemingly endless tight corners.

This is not the environment where a big car is meant to thrive, but it did, and easily. The brilliant steering rack seemed to almost predict corners and its weighting and positivity was so good - and when on a climb, it simply hunkered down over those 20-inch rims and did the business. Turn the sport or sport+ car setting back to comfort and it's utterly composed and compliant. There's not much you can throw at either of these models on the road that they can't handle and for machines of this size and ferocity, that's pretty impressive.

On a race track is the only place to really unleash this car to anything even approaching its full potential.

It still requires a bit of effort and you do get the odd reminder of just how savage the modern M cars can be - even with the plethora of control systems to rein in all that power when you do happen to get it wrong, there's a lot of intervention on offer.

Adaptive suspension, a clever active LSD and the ability to change parameters via the car's on-board computer - faster steering, firmer ride, harder gear-changes, less traction control intervention - isn't exactly a new trick.

But it is undoubtedly very useful, and now there are two "M" buttons on the steering wheel to preset different configurations for how you want to drive.

Track and road, for instance, would be the one that BMW would be keenest for us to mention - it's still insistent that the M cars belong on the track.

But it would be interesting to know just how many of these high-potency, high-value machines ever see a race circuit.

With the intervention dialled down for the track, the two cars exhibited very different personalities. The coupe is undoubtedly tighter than the convertible, although the convertible probably feels better on the road.

When braking very heavily at the end of Lakeside's front straight before swinging through a series of elevation-changing corners, it felt stable, although it did give the occasional reminder that it's over 1800kg and almost 5m long.

So who should be buying this latest German twin-pack?

It's going to be reasonably rare to see these on the road in New Zealand - at $265,100 for the coupe and $277, 100 for the convertible, you're hardly going to run into them at the supermarket on a regular basis.

BMW puts the ratio of tin-top to soft-top about 3:1 for both New Zealand and Australia, and while the coupe is definitely a stiffer proposition when let loose on a track, the convertible is probably the best all-rounder.

If it's just too much show for your liking though, the hairy-chested M5 is a stealthier, and slightly cheaper, alternative.