If you can a get a used one of any of the new models like mid to late 09 you'll pro be best, the new arcades are pretty decent as far as fan sound goes, and the overheating isn't so bad with these models.
But, you will have to by the harddrive. If your going to go for a used pro I'd say 08's aren't that bad, thats what I have and mine isn't that horrible. I've had some issues other than the RROD or e-74. but, nothing I haven't been able to repair myself.