As Rychek says, that is the typical battlefield If it is just for housegaming use whatever you have. But the closer to these goals the better the game in my opinion. (I have a friend who only have a 4' x 4' battlefield and playing anything larger than 1,5k battles is really annoying because you simply do not have any space to maneouvre in. But that is just another factor you have to consider)
We played a 6 player (1500 pts each) battle on a 6'x4' table. It was way too small. The gridlock was ridiculous. Especially when the OnG player put all of his goblins in hoard formations. LOL. That team wasn't happy when they found out how slow a unit moves going backward or when strafing.