You could just do the obvious thing! Get a a less expensive new wacom tablet bamboo for like 50$ that can do anything you want and will let you experiment and not make you invest too much mone. Option a you will use it once and a while and it will be awesome option b you will use it non stop and get very good and realize after a while you need a sharper ride , so you will sale that bamboo and get a fancy shmancy intuitos
I know you stated you want Intuos 3 or later, but I have a large Intuos 2 Wacom Tablet (23.5x17.5). I just decided about 2 days ago that I want to sell it, because I'm wanting to get a newer and smaller wacom. The Intuos 2 comes with the tablet pen and pen stand. And it's in good condition. No problems with it as far as I know. I had a couple offers on it already, but no one seems to be serious about it. How much are you looking to spend?