Blair (and other interested tweeters),
A good starting point is the updated review article that Cornell Lab wrote on scope review in their 2008 Winter Living Bird issue: This is an update of a previous article (2003 I think).

http://www.allaboutbirds.org/Page.aspx?pid=1039#top

Best of luck in your quest. Have fun shopping!

Scott Downes
downess at charter.net
Yakima WA