You already own the best all weather sports sedan money can buy in my opinion. A Boxter is still a very different animal. Mine is a joyride only and still the most fun I have ever had on four wheels. I have zero experience driving my Box in cold weather but there are only two times I don't enjoy driving it:
1. Heavy freeway traffic... mindless low speed clutch, shift, clutch is horrible.
2. When I need to put the top up.
In fact it's about 70 outside with light winds and clear blue skies... I think I'll take her out for a spin.
Good luck in your quest.