Thanks all for the replies and suggested bags; I'll study those linked. Another I found that has an advertised small compression size (8x6 inches) is the Big Agnes Fish Hawk:

http://www.backcountry.com/store/BAG...gree-Down.html

For those of you with compression bags and down sleeping bags, do you find that you compress your sleeping bag down to small sizes like the two I quote (8x6 and 7x7 inches)?