I'm also (always?) in the process of adding gear so, sadly, I have nothing to sell. Have you checked your local craigslist? That's where I scored my latest Canon lens.
I was very patient and lucky when I came across that 55-200 on craigslist.
Note - if you're anything like me and you purchase a USM lens, be prepared to not buy standard again. I'm a bit concerned what will happen if and when I ever buy an IS USM.
Or L.
Also, any reason you're only looking at EF-S when the entire EF line will also work with the XS?