IT may well have been the worst-kept secret among motoring enthusiasts – that the model year 2006 Impreza WRX and STi models would boast a 2.5-litre turbo four in place of the venerable 2.0-litre turbo boxer.

But for a wider audience the arrival of a new Impreza comes down to just one thing – what will the front end look like?

After the goofy "bug-eyed" Impreza of a few years ago, enthusiasts have tended to draw breath and avert their eyes when any new Subaru broke cover. The mixed reception of the B9 Tribeca is proof of that.

Fortunately Subaru’s designers toned down the 2003 Impreza facelift, which took a more conservative styling approach and went some way to redeeming the Japanese-based car-maker.

Now, roll on to 2006 and the latest incarnation of Subaru’s much-talked about WRX.

Despite the fresh new face – somewhat affectionately nicknamed the koala nose by some motoring media – the Impreza is just 55mm longer than the old car and remains largely unchanged except for specification improvements, an engineering makeover involving the engines, gearboxes and some added dynamic refinements.

This mid-life makeover must now carry on until the all-new Impreza arrives around late 2007.

So that means the much-vaunted “aerospace inspired” three-part mesh grille is here to stay across the range, which now includes the entry 2.0i sedan and hatch, RV hatch, 2.0R sedan and hatch (replacing the RS) and range topping WRX and WRX STi models.

We generally like new look but on the WRX and STi it still manages to look too fussy and a little overdone.

However, it can be argued that this sport edginess is precisely what buyers of these performance models want so we’ll graciously acquiesce to their desires.

In profile, the Impreza’s handsome lines continue, with its wheel-arch blisters and chunky door handles. Apart from some new tail-light lens the rear end remains the largely same.

Overall weight has inched up a tad, by 20kg to 1415kg in the WRX, which one assumes is because of the extra weight of the now standard side head and thorax airbags.

In the absence of having any normally aspirated 2.0-litres available, which include the perky 2.0R with its double overhead camshafts and active valve control delivering 118kW of power at 6400rpm and 186Nm at 3200rpm, we were easily coerced into the WRX for a modest spin around the windy mountain roads behind Brisbane.

As soon as you were under way the Rex was like an attack dog straining to be let off the leash.

The power we remember from WRXs of old – rapid and unrelenting - but its seemless and linear delivery from barely above 20km/h really impressed in the newer car.

The newest WRX is less aggressive, more progressive. The same can be said of the all-paw traction in the WRX. It offers levels of grip that can leave passengers spell-bound if they have never experienced four-wheel drive before.

But the price you pay for such acceleration and handling is a firm ride and plenty of tyre noise generated through the cabin.

Even though the Rex’s power output remains at 169kW at 5600rpm it remains an awful lot for a little car. Torque is up 20Nm, or 6.6 per cent, to 320Nm at 3600rpm.

Time and again, the power comes on in a seemless fashion from low down the rev range, making third-gear point-and-squirt acceleration through some windy hills an entertaining experience.

However, because of heavy holiday traffic we had to amuse ourselves running through the car’s revised specification levels – aluminium lower suspension arm in the sedan, aluminium pedals, electronic throttle control, HID headlights with headlight washers, immobiliser, Suretrac limited slip differential, four-pot front and two-pot rear disc brakes and new 17-inch alloys.

All very nice touches complemented now by dual side airbags for the modest ask of $40,990 for the five-speed manual, up just $1000 over the old car. The automatic has been dropped.

Throw in climate control air conditioning, cruise control, sports seats, anti-lock brakes, remote central locking and foglights and the WRX remains a persuasive argument for low-cost, high-performance motoring.

After our modest road trip, we did manage to take the WRX for two hot laps of a race circuit but again it was difficult to come away with any overriding impression that much had changed about Subaru’s star car.

Apart from the more refined power delivery, the clutch and shift linkage quality felt vastly improved – more positive in the gearshift throws and with a firmer, more precise clutch take up.

The car’s drive-by-wire electronic throttle control – all Imprezas get it – allows the Rex to be driven with more precisely measured throttle inputs.

Fans of the traditional throbbing horizontally opposed boxer engine will also be delighted by subtle exhaust changes that have made the Rex more efficient while also delivering a more throaty engine note.

The more aerodynamic front end has also allowed designers to reduce the height of the ‘letterbox’ turbocharger bonnet scoop.

We’ll also have to take it on face value over Subaru’s claims of significantly improved headlight performance for the WRX and STi, which both now feature high-intensity discharge headlights.

Poor headlight performance was a problem with some Subaru models and it’s good to see management doing something about it.

However, the downside is that they are not more widely available across the range.

In our all-too-brief exposure to the latest WRX it is clear Subaru has maintained a build-brief of continuous improvement, refining and improving the things that it really believes count – a car’s dynamics and overall performance.

That’s hardly surprising given the company’s heavily engineering-based manufacturing philosophy, courtesy of Fuji Heavy Industries.

The bottom line however, is that the WRX remains a thoroughly entertaining car to drive.