All you need is get the same size winter tires as you have now on your set of wheels, which I believe is 225/40/18 and 255/35/18. You can also get 225/40/18 all around, even though your rear rims are 8.5" wide vs. 8" on the front, most tires can "stretch" a bit to fit.
I have Dunlop Winter Sport 3D on my xi, and they were great in winter.
If you have very heavy snow in your area, then winters are highly recommended. Otherwise, if it's very light snow that is not frequent (and your area's temp is not very low), then all-seasons should be ok.
MY07 A22 E90 N52Nxi