The Subaru WRX is powered by a 2.0L turbocharged "boxer" 4-cylinder engine. In standard WRX guise, it produces 268 horsepower, which is fed to all four wheels through a 6-speed manual transmission. The WRX STi is powered by a 2.5L turbocharged 4-cylinder and output of 305 horsepower. The STi features the same all-wheel-drive system and a 6-speed manual combination that is so potent in the standard WRX. Sport Lineartronic -- continuously variable automatic transmission -- is available on the WRX but not on the STi. The WRX comes in three trims: Standard, Premium and Limited. Standard WRX models come with 17-inch wheels and a 6.2-inch Starlink multimedia touchscreen infotainment system, which features HD Radio, smartphone integration, a CD player, USB and iPod inputs, six speakers, and Bluetooth hands-free connectivity and audio streaming. Automatic climate control rear backup camera, tilt/telescopic steering, full power accessories and cloth sport seats with driver's 6-way manual adjustability. The WRX Premium comes equipped with heated front seats and mirrors, a power glass moonroof, fog lamps and an aero package that includes a rear spoiler. Limited trim includes everything that comes with the premium trim as well as an 8-way power adjustable driver's seat, leather trimmed upholstery, and LED headlights. Subaru's EyeSight driver assist technology is available on the WRX Limited and includes active safety features like adaptive cruise control, pre-collision braking and lane departure warning. Beyond the bigger engine, the STi differentiates itself from the "regular" WRX with a more aggressive exterior, featuring a unique hood and more pronounced fender flares. The bumpers are also more aerodynamic, giving the STi the impression of a high-performance vehicle. Underneath, the STi backs up this impression with lower, stiffer springs, bigger brakes and larger alloy wheels. The STi comes loaded with features and is available in standard and Limited trims. Standard features include 18-inch wheels spread over massive 13-inch front brakes, a 60/40 split folding rear seat, a leather wrapped flat-bottom steering wheel, a 3.5-inch LCD screen mounted in the instrument cluster and a dual-zone climate control system. Optional across the WRX range is a navigation and Harman/Kardon audio package. Safety features include big anti-lock brakes, traction control and stability control as well as the confidence of Subaru's symmetrical all-wheel drive system.