You'll notice a big difference more smiles and an engaging drive. :-)
Standard forester x 160bhp
Xt 225bhp
Prodrive kit claims up to 250bhp and more torque, with remapped ecu ss exhaust and some other goodies.
My first gen jdm foz was supposed to have around 240bhp when it came out of the factory. 17 years later it still feels fast enough. And pulls like a train. Obviously with the xt you'll have all the fun of a turbocharged all weather car. And the ability to stun people when they see how rapid the normal looking car is.
The ride is comfy and you can push on to a degree, juat got to remember that it sits quite high off the floor so the centre of gravity is higher. An impreza it's not, wben it comes to the corners,
I'm sure the standard x is a great car too and there are member on here who love them. But speak to anyone with a turbo'd car and they'll tell you the boost is addictive :-)
I'd check service scheduals have stuck to and they have treated he car to reguar oil and filters,
As for what to look for i'd take a look in the buying guide as it covers all subarus.