Luxury, Meet Agility

When can you call a 4,160-lb. (1,888-kg) fullsize sedan nimble? When it's packing 425 hp from the all-new Hemi 6.1L V-8 found under the hood of the '05 Chrysler 300C SRT8.

The 300C SRT8 is the second vehicle in the Chrysler stable to wear the badge of the SRT performance-tuning unit, following the Crossfire SRT6. Designers were careful not to go overboard on the styling, largely because the Chrysler-brand interpretation of the SRT performance formula is more subdued than that of the extrovert Dodge-badged SRT models.

The brunt of SRT's development efforts can be found underhood, where the new 6.1L displacement for the lauded Hemi Magnum OHV V-8 powers this elegant, yet brutish, sedan.

This rendition of the Hemi produces 425 hp (an 85-hp jump from the “original” 5.7L Hemi's 340 hp). That's almost 70 hp/L — a specific output that places the hi-po Hemi ahead of the smoking 4.6L SOHC V-8 in Ford's new Mustang (65 hp/L) and neck-and-neck with rival General Motors Corp.'s. Cadillac Northstar 4.6L DOHC V-8 (70 hp/L). Torque is 420 lb.-ft. (569 Nm) at 4,800 rpm, 30 lb.-ft. (41 Nm) more twist than the 5.7L.

SRT engineers increased cylinder bore by 3.5 mm (0.14 ins.) to obtain the 6.1L displacement. Oil squirters were realigned to aim at the underside of each piston, to aid cooling, while the pistons themselves were redesigned to include a larger diameter, flattop design to meet the 6.1L's increased 10.3:1 compression ratio.

Intake valves were redesigned with hollow stems and 2 mm (0.08 in.) larger heads than the 5.7L, improving airflow. Exhaust-valve stems are filled with sodium to help dissipate heat more efficiently. These, and a few other tricks, help the Hemi move the 300C SRT8 from 0-60 mph (97 km/h) in the low 5-second range.

On the outside, SRT's designers worked to make the 300C SRT8 unique with subtle changes, including new front and rear fascias to direct airflow though lower ducts to cool the brakes, while a new integrated rear spoiler helps to increase downforce by 39%.

The interior also benefits from minor upgrades, the most notable being the sport seats, with increased side bolstering and suede inserts to keep the driver and passenger firmly planted.

Changes to the ride and handling include retuned dampers, specially tailored spring rates and suspension bushings, along with larger diameter sway bars. New front and rear suspension knuckles help to lower the 300C SRT8 by 0.5 ins. (1.3 cm), while the electronic stability control is retuned for performance handling.

Gunning the 300C SRT8 through the desert backroads near Scottsdale, AZ, it is evident the tweaks have dramatically changed the character of this sedan from its slightly more pedestrian 300C sibling.

On the desert's undulating roadways, the 300C SRT8 hunkers down and begs for more velocity. Thundering along at more than 120 mph (193 km/h), the SRT8 is inspiringly pinned-down through the twists and turns.

On an autocross course, tires squeal and the recalibrated ESC doles out prudent tastes of the surprising and determined cornering ability SRT has baked into this fullsize car.

The 300C SRT8's $39,995 base price is the ultimate equalizer. The cost is nearly half the $79,500 base price of the E55 AMG. On a performance-for-dollar scale, the 300C SRT8 may be the most logical buy in the performance-sedan segment.