My suggestion, DO get the sports package 370Z. You'll love those big brakes and nice little add ons available on the sports package. THEN,
Buy a set of dedicated winter rims/tires:
My Winter Rims/Tires Setup: TRMotorsport C2 + Blizzak LM-25 w/TPMS w/pics (AK370Z)
These will take miles off your summer tires (you can go more summer seasons with same tires) and will give you serious traction in snow. I am a big time blizzaks fan. I'm LM-25 but they are discontinued. You'll be fine with the LM-60. With these tires, you can clear as much snow as your front bumper will clear (which is about 4-5"). Anything more, you start to scrape front bumper. Also, make sure you get narrow rims and tires (that'll still clear the AKEBONO in sports package) for snow.
Good luck. We are always here to help you.