IMHO stocking foot waders are no good for extreme cold weather. When I used them my feet were always cold. Bootfoot neoprene 5mm are great for keeping you warm. Buy them a boot size larger. Fleece Fleece Fleece. wear in several loose layers but not so loose your swimming in them. I do like a silk base layer though. Finish off with a wind/waterproof jacket and hat and you'll be warm all day.
I think a 9wt. is a little heavy for most of my steelhead fishing but it depends on the water you fish and how big the fish are. The bigger the water and fish the bigger rod you will need. For all around use I prefer a 7wt but if a 9 is what you have you should be fine as long as you don't use very fine tippets.
Turk