my bro has a 2006 Liberty GT tuned by STi
it's a fair bit quicker than my stock C34 RS Four S (factory manual), and handles and stops a lot better too
it would want to for the $70k he paid for it (brand new)
a few mods to the Stag (as above, air filter, exhaust, nistune etc.) and it'd probably win in a straight line, but would still struggle in the twisties
i bought my Stag from Nagoya too. not super happy, but not sad either
the Stag is more of a GT car, than a race car
if you want something quicker that handles better, grab a Toyota Caldina. a mate has one, and if it was as big as the Stag, i'd have bought one (i have a newborn so need to lug around a pram, cot, luggage and golf clubs, and the Stag swallows that up easily. a Caldina would struggle to carry that much)
hope the above helps