I think I did a post a while back about me nearly buying a 17 foot Dell Quay Dorey (an oldish one) - what put me off (apart from buying a sailing boat!) was the foam core and not being sure I could spot that it was becoming waterlogged.
I probably mentioned things more in depth on my previous post(s), so you might want to do a search (I hate it when people say that!).
Dave - its unusual to get a survey done when buying a used boat of that size. My preference would be the Boston Whaler though.
When you think you have found a boat that you like, post all of the details here, including the type of boat, engine, age, general condition, trailer, in fact the whole damn shabbang. We will then all contribute our bits to advise (hopefully!).