Does this only happen at start-up, or the entire time the car is being operated?
I've experienced the strong gas smell in cold temperatures with my Sube as well, but only at start-up. Once the car is warmed up/at operating temp the smell goes away. In the absence of any identifiable source, I just chalked it up to a richer fuel/air ratio being used when the car is started in cold weather (of course I have no idea how true this might be...I can come up with all sorts of baseless theories to explain away things I don't understand).
I had also heard about the fuel line issue...essentially the fuel lines contract in cold weather, resulting in leakage, but was told that this issue had been addressed with my model year (06).
You could check out www.ultimatesubaru.org for info specific to your car.