Polish for "party," the Impreza is a sporty, all-wheel drive, compact sedan or wagon with a focus on performance, particularly in its racing-oriented WRX models.  Some engine changes, exterior tweaks, and renamed trims are the major changes for the 2006 Subaru Impreza.  
The base model has been changed from the RS to the 2.5i and is powered by the 2.5-liter, flat-4 engine at 173-hp.  Nothing too exciting. The good news for driving enthusiasts is the new turbo 2.5 DOHC flat-4 in all WRX trims, which gets 230-hp in WRX, WRX Limited, and the new WRX TR.  The speedy WRX STi uses the same engine to hit 300-hp.  Torque peaks much sooner in the WRX lineup, and new brakes and improved steering ratio add to the performance enhancements. A 5-speed manual is standard across the line, and a 4-speed auto tran is optional on the base model.  The WRX STi comes with a 6-speed manual only.
Also new in the 2006 Impreza is a new WRX TR, which is a pared down and less expensive WRX, combining racing performance with the basic features of the regular 2.5i.  Like the STi, it comes in sedan only.  All other WRX trims and the 2.5i come in sedan or wagon.  There is also an Outback Sport wagon.  The new WRX Limited is a luxury version, with heated leather seats, power sunroof, and heated mirrors.  
On the outside, the 2006 Impreza gets a the new tri-section mesh grille, new taillights, and new headlights.  The STi reduces the outlandish size of its hood scoop.  No surprise that the WRX engine is a crowd-pleaser, offering lots of power and speed.  Acceleration is immediate, handling and maneuverability are top-notch, even in the 2.5i.  All-wheel drive is always rated highly.  Complaints focus on the small backseat, a noisy engine, a subpar stereo, and cheap-looking interior materials.