The one concern I have with that Dell OptiPlex is that it appears that it has only VGA video connection, and not any modern digital connection. I'm not sure how much that matters, but I've heard a number of people say that it's better have DVI-D as a minimum for a modern flatscreen monitor. Even if the current monitor is CRT, it's a good idea being ready for anything.
A video board could be added, of course, but that adds to the cost later on. Plus a mix of research, and looking at that photo in the Amazon listing, suggests that this computer would use "low profile" boards. I'm not sure how common these are, but when I was looking around for one for my current computer, I got the feeling they aren't as common as regular boards.