There are 7 generations of the Subaru Legacy but the 3rd generation is the when GT limited trim level was added to the fleet from 2000-2004. The 3rd gen legacy GT (BE chassis) came with multiple engine options ranging from the Naturally aspirated EJ251 ,the Japanese EJ206 twin turbo, and the flat 6 EZ30. Between all the options for motors the 3rd gen legacy gt could make between 125hp-289hp with a curb weight of 3300lbs.
The 4th generation legacy GT was built from 2005-2009 and came with the EJ255. This generation came equipped with either 5 speed manual or a 5 speed automatic. In 2007 the 4th gen Legacy GT got face lift and some upgrades that includes The Newley adopted SI Drive allowing you to change the throttle response for fuel efficiency as well as allowing you to control the center diff. This generation was the first to introduce the Spec B Trim in 2006 which essentially tuned the Legacy Gt into An STI on a different chassis, it came with ej257 and the 6 speed manual. There were only 497 Legacy GT Spec B’s released in 06, 3000 in 07, and only 51 between 08 and 09. This was the only generation for the Spec B leading them to be desirable and rare to enthusiast. between the two GT trims this generation could make 250hp-310hp.
The next 2 Generations did not have a GT model only came with a 3.6L flat 6 or the 2.5L flat 4 with a 5 speed auto or CVT. Lastly the 7th generation starting in 2020 Changed the GT name to XT like the Forester XT. The new XT model is coming equipped with the FA24 Subaru’s newest boxer motor replacing the EJ257 after its 25 year production life span. unfortunately this Legacy XT will only come with a CVT leaving it undesirable for manual enthusiast. this generation makes about 260hp.
The best generation of Legacy GT is the 2007 Spec B due to the fact its the most available with 3000 made, equipped with all the new technical features (SI drive) and most power GT model from the factory, it is most certainly driver oriented with 6 speed manual out of the STI.