Last year I was in a pinch and needed some cold weather pants quickly for an Iron Butt ride. I bought a pair of Bilt Storm 2 over pants. I'll be honest, I haven't tested the waterproofing and can't comment on that. Otherwise, they have been a killer bargain for less than 200 bucks.
Heavier material on the inner legs to prevent exhaust burn, removable quilt liner, and they zip far up the leg so they can be put on/taken off easily while still wearing boots. I've done a handful of Iron Butt rides with these pants down in the 20's. A heated layer, regular pair of jeans, and these pants work great. Obviously heated gear goes a long way but these pants still provide great wind protection and insulation even at 80MPH/25 degrees. If it's at least above freezing, wearing only jeans under these pants is fine, no heated gear needed.
My eventual plan was to get a nice pair of Klim pants. I am going to wait until these are worn out, they are doing fine.