Hmm, methinks this should be in the folding bike section..
[EDIT]: oops, too late its already there..
anyway, to redryder74 - if you are not comfortable with the brompton when you tried it then put the 16" folders out of the list since it will be the same thing.. what are you more concerned about with the weight - the 8 mile route or the two flights of stairs? because if I have to choose I would go with the Jack since it has bigger tires so that means the ride wouldn't have much vibration compared to other models, and those 2 flights of stairs wouldn't be a concern as long as I'm not running upstairs with a 30-pound bike..
why not try those models you mentioned in your LBS - that would help you with your decision..