intuos 3
don't bother with the 2, it's a massive step down, don't both with the 4 as the 'textured' surface wears down nibs faster than usain bolt
the 5 is pretty awesome but expensive as it's brand new, get the 3- but they came before the whole wide screen thing, so they're sized based on A4, A5 etc, but they also came in a 'wide' version, I have the a5 wide and it's perfect for my 26" monitor
a4 is also nice but it's a lot of arm work to move about the surface, good for precision though, so make your choice