Don't focus on frame material. Instead test ride a bunch of different bikes, and then buy the one that fits best, rides best, appeals to you, and hurts your wallet at an acceptable level. With respect to carbon fiber bikes, they don't necessarily ride better or perform better than aluminum bikes, steel bikes, or titanium bikes. The design, construction method, and QC are way more important than the type of frame material. I would suggest that you try both WSD bikes and appropriately sized men's frames. A WSD bike is just designed to fit a statistically average proportioned woman according to a given company's sizing standards. That doesn't mean a given WSD bike will fit your unique self better than a men's bike. I went through this a few months ago with a friend's wife. Over the course of visiting 5 LBS, she tried a lot of bikes, some WSD, some not. As you might expect, some WSD bikes worked ok, while some men's bikes worked ok. As it happened she ended up with a WSD bike, but the difference between that bike and her second choice, a men's bike, was very small. At a given price, there's not going to be a great difference in components between bikes from different manufacturers. That's mostly true. Still, given a price point and bikes that ride and fit well, it definitely would behoove you to buy the bike that has the better components. Note that you can get bikes from a previous year that were more expensive but are now priced low. This is the time of year to be looking for such deals on models from past years because dealers are looking to clear the old models off their showroom floors to make room for the new models. I'd say the next two months are the best time to look. Buying used can save you a lot of money, BUT you need to know what you're looking for and at. You don't want to get stuck with a bike that was busted in a way that will soon render it a lemon for you. Unfortunately, some carbon fiber failure mode are difficult to detect visually. If you are going to go the used route, I'd suggest taking someone who knows about bikes with you. If that's not possible, you might insist to a potential seller that the bike be inspected at an LBS. Quite a few LBS also sell used stuff, so that might be a safer option than buying from an individual. Sizing: the most important dimensions for a fit are head tube length and reach (the distance from a vertical line through the bottom bracket to the head tube axis of symmetry. Most LBS and manufacturers don't state reach, so instead you have to rely on virtual top tube length and seat tube angle (and of course the aforementioned head tube length). Note that for a given top tube length a steeper seat tube angle will result in a longer reach to the handlebars. If you're old Trek still fits well, you can use the dimensions of that bike as a reference.
