I'm trying to put together a basic clothing list (assuming temp range encountered on a thru). Some previous posts have suggested getting a 100wt fleece top, in addition to a down jacket. Is this necessary? Assuming I have a lt/wt and a md/wt polypro top, the 100wt fleece and some sort of wind shirt, wouldn't that work? Can you layer both a ltwt and a mdwt top? I think the biggest concern is that while down jackets sound great, they are also a major tax on the wallet (costing nearly what my sleeping bag does)--not to mention the 10-23 odd ounces it can add... what do you think?