Just remember whatever you buy that the temp listed is a survival rating and not a comfort rating. The comfort rating is usually 10-15° higher.
For under $200 you can't beat the U.S. military ECWS sleep system:
One of OSA's sponsors sells 'em: http://www.greenbeetlegear.com/us-military-4-piece-modular-sleep-system-brand-new/
Scalable to your environment and rated into the negative temps with the right undergarments.
ThinkGeek has taun-taun sleeping bags... Like a boss
Enter your email address to join: