Agreed that new is the best, but a used one is only $139.99 at GameStop. $170 gets you the 20GB model, while $200 gets you the S model, but only with 4GB of memory. In any case, it's a good deal whichever you choose.
Local game store near me has a great deal, buy any used console (prices are equal or below GameStop) and you get a buy 1 get 1 free deal on used games. So $130 360 + used $30 game + free game usually priced at $30 = $40 less than a new 4GB model, leaving $30 spare for a game or a 16GB USB stick.