With the hardtop raised and symphonic sound swirling through the leather-lined cabin, this car cruises in the insulated Lexus mode of quiet motoring supported by dazzling electronic wizardry and effortless controls.

With the top stowed and fresh air flowing around the cockpit, you can put your foot in it and response is immediate with the force of 300 horses. It can rip down a straightaway at an illicit pace, but also cut through a mess of off-camber mountain curves with the dexterity of an athletic sports car.

We surfed along beach boulevards around San Diego in convertible mode with the stereo cranked high and a California sun baking leather seats. The only thing missing from the drop-top ride was a wind-battered hairdo, as the aerodynamic engineers at Lexus somehow managed to deflect the air flow away from the cockpit. Even at high speed, you feel little wind and can conduct a conversation with a seatmate without raising your voice.

Then we sealed the top for a run across pine-covered mountains east of San Diego to the low Anza Borrego desert for speed and agility experiments. Despite the luxurious accommodations and an elite quietness in the cabin, the car revealed an aggressive character that only becomes evident when you press it hard and swift through a wiggly route or run flat out on the desert floor.

The squatty stance sets up a flat-footed posture in the manner of a classic sports car with all of the right ingredients aboard: A rigid platform with stretched wheelbase, brief body overhangs front and rear, good weight distribution with the engine mounted up front and all torque applied to the rear wheels, plus independent suspension for all wheels and quick-to-respond rack and pinion steering.

That big engine, an aluminum quad-cam V8 measuring 4.3 liters, musters 300 horsepower at 5600 rpm and as much as 325 foot-pounds of peak torque at 3400 rpm. It's enough to hurl the SC 430 from 0 to 60 mph in 5.9 seconds and send it to the quarter-mile post in 14.4 seconds. The top speed, guaranteed to peg the radar needle of any law enforcement official, hits 156 mph.

All the muscle channels through the automatic five-speed transmission that shifts discreetly with Lexus efficiency. It has three programmable shift modes (normal, sport and winter) and a gated shifter mounted on the floor console. Thanks to the C-shaped gate track, a driver can accurately flick the stick through all five gears for selective control that approximates a manual -- or leave it alone to make its own intuitive shift decisions.

The SC 430 also carries a complete complement of electronic controls to keep the wheels tracking safely straight. The anti-lock brakes link to traction and vehicle control systems that check tire slippage both forward and laterally. In severe corners entered too fast, we noticed a slight push from understeer followed immediately by oversteer. But that was easy to predict and was corrected automatically by the vehicle control sentinels.

Alloy wheels of 18-inch diameter are the largest ever from Lexus, and they carry low-profile Dunlop performance tires monitored by a tire pressure warning system. Run-flat tires by Bridgestone or Goodyear are optional, which eases trunk space by deleting a spare tire. However, the run-flat option introduces a ride quality that's slightly rougher and more noisy than the Lexus standard.