Luxury sport sedans have long been the exclusive stomping ground for the high-end European manufacturers. Challengers from Asia have managed to chip away at this market segment over the years, thanks to a steady evolution of better products. For a prime example, look no further than the 2009 Infiniti M45.

The V8-powered M45 offers performance and luxury comparable to that of the venerable German marques, all while sparing a healthy amount of cash from the bottom line. The midsize Infiniti also delivers an astounding amount of technology that enhances nearly every aspect of the driving experience. Adding to the appeal is the availability of the all-wheel-drive M45x.

With the M45's smaller-engined M35 stablemate arriving on the scene this year with a reworked V6 power plant, a sibling rivalry seems inevitable. The M35 now produces more than 300 horsepower and exhibits nearly identical handling prowess, so the dividing line within the M line has been blurred. As it stands, either of these Infiniti Ms proves worthy of consideration against stalwart luxury sedans like the BMW 5 Series and Mercedes-Benz E-Class as well as other desirable entries like the Jaguar XF and Lexus GS.

The 2009 Infiniti M45 is a midsize luxury sport sedan available in two well-equipped trim levels. The base model M45 and the all-wheel-drive M45x have standard features that include 18-inch alloy wheels, adaptive xenon headlights, a sunroof, keyless ignition and entry, leather upholstery, 10-way power front seats with heating and cooling, driver-seat memory settings, dual-zone automatic climate control, Bluetooth and a six-speaker audio system with a six-CD/MP3 changer and an auxiliary audio jack.

Options are grouped into packages with slight variations between the M45 and M45x. The Sport package, which is not available on the G45x, includes 19-inch alloy wheels with high-performance tires, sport body styling, rear active steering, a stiffer sport-tuned suspension, aluminum trim that replaces the standard wood accents and sport seats with added side bolstering. The technology package adds a hard-drive-based navigation system, an upgraded eight-speaker Bose sound system with a 9GB music server, a rearview camera, iPod connectivity and voice-activated controls. An advanced technology package can be added that includes a premium 14-speaker surround sound system, a lane departure warning system and adaptive cruise control.

A mobile entertainment system is available in conjunction with all previous packages, but only for rear-wheel-drive M45s. This package basically consists of a rear entertainment system. Finally, a premium package is available that includes all of the previous packages (minus the sport package) and adds heated and reclining rear seats, rear air-conditioning and audio controls, and a power rear sunshade.

The 2009 Infiniti M45 is powered by a 4.5-liter V8 that cranks out 325 hp and 336 pound-feet of torque. The standard transmission is a five-speed automatic featuring manual shift control and rev-matched downshifts. Fuel economy comes in at an EPA-estimated 16 mpg city/21 mpg highway and 18 mpg in combined driving. The M45x drops slightly to 14/20/16 mpg.

The Infiniti M45 comes standard with antilock disc brakes with brake assist, stability and traction control, front-seat side airbags, full-length side curtain airbags and active front head restraints. The advanced technology package adds safety features including an advanced lane departure warning system that alerts the driver of unintended lane drifting, then applies light brake pressure to specific wheels to maintain lane placement. Also included is an array of sensors that detect an impending crash and tighten the seatbelts. The Insurance Institute for Highway Safety gives the M45 its highest mark of "Good" for frontal and side impacts.

The 2009 Infiniti M45, with its potent V8, provides plenty of power for most drivers. Considering the M45's superb handling capabilities, the ride quality is surprisingly comfortable and compliant -- though some with a penchant for full-luxury cars may find it a bit harsh, especially when equipped with the sport package. On the open highway, road noise is kept to acceptable levels, but the M45 is not as silent as a competing BMW 5 Series or Mercedes E550.

Infiniti's M45 has a spacious cabin that comfortably seats four adults. Materials quality is first-rate, with rich leather and pleasing wood appointments. Even in base trim, the front seats are firm and supportive, with plenty of power-adjustable settings. Opting for the Sport package enhances the M's athletic nature by adding racier seats with more aggressive side bolstering and race-inspired accents throughout the cabin. The gauges are bright and legible, but the center stack controls are a bit busy, with a dizzying array of buttons. Even so, you'll probably find them easier to operate than some of the menu-based systems on German luxury sedans.