Subaru today unveiled three higher-performance versions of its Impreza WRX and WRX STI models at the British International Motor Show. All include engine upgrades that boost horsepower and were performed by Prodrive. In addition to the power hikes, the cars also feature interior and exterior changes to differentiate them from lesser models.

The company’s WRX model receives a 28-horsepower hike to 252hp thanks to a revised exhaust system and tweaked ECU from Prodrive and in the process becomes the WRX-S. The real benefit is the bump in torque, as this grows by 51lb-ft, to nearly 288. Subaru claims these changes are good for a 0.6-second reduction in the 0-60mph time, now claimed to be 5.5 seconds.

Subaru says the car has £4,500 worth of extra equipment, but it is priced just £2,500 higher than the standard WRX model, at £22,495. The added kit includes 18×7.5-inch (up from 17s) anthracite GT1 alloy wheels surrounded by 225/40 tires, an STI front grille, STI front lip spoiler and STI wing and body-color tailgate molding. Inside, a MOMO Air-Race shift knob is the only addition.

The next step up is the Impreza WRX STI 330S, which is based on the 300hp STI model. Again, a Prodrive Performance pack boosts power by about 25 points thanks to an ECU re-flash and exhaust system, but the larger 3.5-inch exhaust also uncorks Subaru’s signature flat-four burble. The torque gain accounts to 46lb-ft, and now peaks at nearly 347 and about 600rpm lower. The 0-60mph sprint is now over in 4.4 vs 4.8 seconds, Subaru claims.

Visual additions to the car include leather Recaro seats up front, a satellite navigation system, and a Smart entry system with push-button engine start. Different 18×8.5-inch wheels shod in 245/40-18 tires are fitted as well. The price for the 330S, at close to £30,000, is about £3,400 dearer than the standard-spec STI.

Both the WRX-S and are expected to arrive at dealers in the U.K. this September.

The STI 380S is still in concept form, and no photos were provided. It is expected to launch within six months, but only if the public reaction is deemed positive enough by Subaru. Pricing is not yet known. It will, however, bring 375 horsepower to the table with the addition of more Prodrive components in addition to an engine rebuilt with stronger internal parts and will be built to order as the customer wishes. Different suspension, exhaust and a unique body kit will be part of the package. Rolling stock will consist of 18-inch BBS wheels and 245/40-18 rubber.

The models are seen as the answer to Mitsubishi’s FQ range of Evolutions, including the 290-horsepower FQ-300, 324hp FQ-330 and 354hp FQ-360.