I disagree (slightly) with the previous posters. I think a 7 weight is a a better size for smallies. Not so much to fight the fish but to cast large flies - big wooley buggers and clousers. Some (Harry Murray) even recommend an 8 weight.
I agree that the St. Croix Avid is a good choice. I own a St. Croix Legend Ultra 5 weight that I use on big rivers out west - it is good in the montana wind.