Here's a great post on doing the math for this stuff

http://blog.asmartbear.com/easy-statistics-for-adwords-ab-te...

But yes, the bad news is it's going to take too long at your rate right now. I recommend looking at things like http://conceptfeedback.com to get feedback in lieu of being able to test right now. You could also consider running a poll with Mechanical Turk workers. The turkers would answer a poll like which design is better for about a $0.05 a person.

I've done the conceptfeedback.com for testing some new elements in http://tgethr.com before we had the traffic to start experimenting and the feedback was great.