On the outside, Hennessey keeps the modifications to a minimum with a few SRT600 badges and optional 20x10.5-inch forged-aluminum wheels wrapped in grippy Michelin Pilot Sport 2 295/30ZR20 tires (not shown). The factory SRT-spec Brembo disc brakes already work well so they remain untouched. Inside, there are specially embroidered Hennessey floormats, SRT600 badging, and a serial-numbered dash plaque.

Cruising about town the SRT600 is mellow until you crack the throttle, the W5A580 five-speed downshifts, and the turbo's boost fills the intake manifold. Then the SRT600 violently lurches forward, floor the SRT600 and all four tires spin and shriek. On a sticky dragstrip, the Jeep's 20-inch tires hook up as the 4800-pound super 'ute runs 0-to-60 mph in 3.4 seconds, 1.4 seconds quicker than stock. The AWD SRT600 is so quick off the line, it out-accelerates a stock Viper by more than a car length at 60 mph. Once you've beaten your buddy's SRT10 Viper in the quarter mile, you can head to the pits to load the kids in the car seats, fill the back with supplies, and drive to the snowy mountains for a ski trip. Try that in a Viper or a Vette.

Performance does come at a price, however. Hennessey's Jeep SRT500 package will set you back $9995; the 392-cube stroker SRT550 package tallies $17,950; and a full-monty turbocharged SRT600 requires a $27,900 dip into the kids' college fund.

Hennessey Performance

2006 Hennessey Jeep Grand Cherokee SRT600
Base price $40,800
Price as tested $68,700
Vehicle layout Front engine, AWD
Engine 6.1L Hemi V-8, OHV, 2 valves/cyl
Transmission 5-speed automatic
Wheelbase, in 109.5
Length x width x height, in 195.1 x 84.3 x 66.7
Curb weight, lb 4888
GVWR, lb 6050
Payload capacity, lb 1150
0-60 mph, sec 3.4
Quarter mile, sec @ mph 11.9 @ 115.6
60-0 mph, ft 123