I've been riding a Trek 2000 WSD for three years and absolutely love the fit (I'm 5'2"). I bought it with the entry level STI components (RSX, on the same level as Tiagra), but just this past spring, I upgraded to Ultegra components. The nice thing about the Trek2K is that it's got a quality, upgradeable frame. In fact, on my bike, the only thing that's original IS the frame. I've upgraded everything else. FWIW, the STI shifters and rear derailleur on the 2002 model are Shimano 105. For a few bucks more, you can get the 2200, which is equipped with Ultegra components.
Of course, the most important thing is which bike fits you, but for someone of our height, a women's specific frame is a good starting point.
Sue