Need help for Hokkaido costs...

[Kagetsu]

I'm stuck with my next choice for Hokkaido, and want to know if it's worthwhile forking out for a rail pass for Hokkaido as I'll be renting a car for most of the time there.

My plan is to get to Sapporo (via Hakodate underground thingo) and from there, head via train straight up to Wakkanai, which will be the start and finish of my car driving trip around Hokkaido... as a lot of places I want to go are hard to get to without a car.

I'm looking for a cost of the ticket from Sapporo to Wakkanai on the Super-Soya train.

That's really all I need to know. ^_^' Also what are the rails systems like in Hokkaido during winter... the JR site isn't very helpful.