You can't argue with more horsepower, more torque and more gears to put them through. Not in this segment, you can't. The larger, more powerful V8 engine that comes in the 2007 Mercedes SL550 rips through the gears in the new seven-speed automatic at a furious rate, if you want it to. When you prefer to cruise, it just sits back and relaxes, upshifting and downshifting silently.

The new V8's exhaust system has been re-engineered to give a much more throaty, sporty sound at wide-open throttle. It settles into a nice burble at cruising speeds. While most German cars are limited to 155 mph by an industry agreement, how quickly you get there is another matter entirely, and the SL550's V8 will get you from rest to 60 mph much quicker, in about 5.5 seconds. Every chance we got, we mashed the throttle pedal down into the carpet at stop signs and traffic signals, and the electronic systems allowed about two turns of the tires before taking over control and keeping the car pointed straight ahead, every time, like launching a rocket. Very confidence-inspiring.

In terms of steering and handling, the 2007 SL has even more chops. The steering ratio has been quickened up so that left-right transitions happen more quickly, there is more feel in the system at the steering wheel, and it tracks better. The second-generation Automatic Body Control (ABC) active suspension system, now standard equipment, has been altered radically, so that it controls body roll, pitch, dive and yaw about 60 percent tighter than the original system, and makes fast driving on challenging roads a very rewarding experience, without beating up the two occupants with a rough ride.

We've also driven the silky smooth S600 with a 510-hp V12 that packs 612 pound-feet of trip-shortening torque as well as the SL55 AMG with a V8 also rated at 510 horsepower, but with a mere 531 pound-feet of torque.

Which model? The SL600 is the one we would buy if we could afford it and justify its price. Its quiet, smooth demeanor, the refinement of the ride, along with its incredible performance (0-60 in the low 4-second zone) and brilliant handling make it the ultimate of luxury sports car. Its turbocharged 5.5-liter V12 engine boasts 510 horsepower and 612 pound-feet of torque. It's paired with the heavy-duty five-speed automatic to handle the huge torque output of the engine.

The SL55 AMG, with supercharged power, lightning shifts with or without the manual shifter paddles, completely different ABC suspension calibrations, bigger, more powerful brakes, and huge tires, is rougher-riding than either the 550 or the 600, with 0-60 times of about 4.5 seconds, louder at the exhaust tips, but oh, so much fun to drive, so much more masculine looking, and more agile than the other two versions on a country two-lane road. The supercharged 5.5-liter V8 engine gets more power for 2007, to 510 horsepower and 531 pound-feet of torque.

The SL65 AMG is the quickest SL of them all, accelerating from 0 to 60 mph in just over four seconds flat. It uses the 6.0-liter twin-turbo V-12 engine, rated at 604 horsepower and a staggering 738 pound-feet of torque. Regrettably, we have not driven the new SL65 AMG.

The sensible SL to buy, if buying an SL can be sensible, is the SL550. It delivers plenty of performance. Its new 5.5-liter double-overhead-cam, 32-valve V8 engine delivers 382 horsepower and 391 pound-feet of torque. That's 80 additional horsepower and 52 foot-pounds more performance than the previous SL500, a car that was already quick. And the more expensive, more powerful models don't get the SL550's new seven-speed automatic.

All the versions we drove had enormous acceleration, but they also had huge brakes with ABS, EBD, ESP and traction control, enough braking power to pull down small buildings with a single stomp, with excellent pedal modulation and linearity.