If you drive alot or like spirited driving go with the X-Fire. If you just want a daily COMMOM commuter take the BMW.
I dont say much for the RX8. Its a great looking car, but i dont trust rotary's the previous gen. RX7 was a nightmare i dont know how the new Renesis engine will turn out, however i've notice the RX8 is a bit overdone. They have placed the rotary triangle on virtually every part of the car, front end, seats, etc.
The quality is good but not great look at the headlights they are just plain cheap. The front is great but the rear looks like the owner himself took charge in his garage with some aftermarket parts. The rear seats are TIGHT and NO TORQUE. Reminds me of my S2000, you have to rev the hell out of the mazda to get it to move and reach its soooo called 5.9 sec to 60 mph as the mags claim, otherwise your in the mid to hi 6's. Load the car up with 2 more people and those times climb.
Sorry but lack of torque in a car is a NO NO to me. And you dont want to be revving your engine at 7500 rpm or higher in city driving to get your car to move you want that to happen around 2 to 3K rpms.
The BMW is just plain boring. NOTE: Dont want any flaming remarks from BMW fans here. Its just a nice 4 door euro sports sedan that is overplayed and they are a dime a dozen here in S. Fla. If i had to go with a 325 i'd go with the 330 Coupe. There the power is about equal to the Crossfire, but the 325 is not as powerful as the X-Fire.
the 350z or Audi TT are great comparisons for the X-Fire not a BMW 325i. The RX8 is also a good competitor but i cant quite swallow a true sports car with 4 seats its still mind boggling that added weight of passengers kills performance numbers.
Also the X-Fire would give you a unique car. Rare, not too many on the street, great performance and handling for what it is a touring car cuz its no tire melting Hot Rod but its got more than enough power to make you smile, great exhaust note and a drop dead styling that no car out there can match IMO. Best of all its got lots of Mercedes goodies in it which speak for themselves.
Just my 2 cents.