Would it be a good idea to get like 28 or 30c cross tires and use them for better traction when it snows or are the usual 25c road tires i ride better?

There seems to be disagreement about this, but I firmly believe that wider is better for serious snow riding. I have a pair of 26"x1.95" MTB tires that I've found to be great in the snow. They're better than anything else I've tried (although I've never used studded tires.) Ask around, or just get the widest most aggressive tread pattern you can. Better yet, get an old mountain bike if you really want to ride through the white stuff.

*Edit* Here they are:

I think it depends where you live. I commuted daily all last winter on 23c road slicks and I only went down once. This was columbus ohio. not too much snow.

Studded tires are for ice. They won't help you on snow unless it is packed. Tread and width is better for snow.

For more info, check over in the Winter Cycling forum.

Of course you can ride 23c tires in light snow but it sucks. For real snow, you want knobbies....the wider the better. Note that studded tires are important for ice...but they are worthless in the snow. Buying yourself an old rigid MTB is a good idea. I take my SS MTB out everytime it snows. Getting out before the roads are plowed is a blast. Riding singletrack in fresh snow is even more of a blast.

I use a rigid fixed mtb with wide studded tires in heavy snow/ice.Otherwise i stay on one of my other bikes(23s-28s).The only time i dropped a bike in the winter was turning into a unsalted sidestreet and hitting some black ice.