I'm curious if some of the people commenting here have driven a twin yet. I sold my M3 for one and do not regret it. I have also owned a 328i and 335i. I see people saying that the 325 is the same performance wise. You are wrong. End of story. Not trying to be a dick, but my BRZ out performs my M3 every time I'm at the track(autocross, not circuit or anything). There are things I miss such as the strait line power or orgasmic exhaust note the screaming V8 yields, but I do not regret getting the Subaru. It really depends on your driving style.
I will say one thing. The stock tires on the Subaru are trash. They are purposely built with the "prius tires" so the car can drift on command. I replaced them a week after I bought the car with some decent tires, nothing fancy, and it really brings the car to life.
I understand the Op was comparing the 325 and has most likely made a decision since this thread is a bit dated. However, do not be fooled by the numbers you are seeing with this car. It is amazing. Bring on the flame!
(ok, so I do sometimes miss the M
)