Just a word of advice - choose a heater that has the highest BTU output. 3,000 isn't a heck of a lot for those cold days. The cool thing about the Mr. Buddy Portable is the ability to switch from either 4,000 or 9,000. Great to have the option. When it got really cold, I would run it at the highest setting for a while to get it toasty, then back it off, or shut it down altogether. With a 3,000 BTU, you'll be running it all day just to keep warm. My HT hut is a Magnum Two-Man. I wouldn't run anything less than a heater that allow me to go as high as 9,000...
(As an aside, I had one of the Coleman heaters a few seasons ago. Can't remeber the exact model. It only lasted a few outings until I realized it was way underpowered...)
In the case of staying warm, the best advice is to go big, or go home..(BTU's that is!

Good Fishing,
Justin