Sarah,
If you are looking to save a little money you may check out Aqua-Safe Systems on Ebay. They have a good product. I got one I think they called the Monster or something like that. It has 3 pre-filters, RO, DI and a carbon after filter, 4 gal tank, and drinking spigot for your sink for $125 which INCLUDED the shipping.
And they got it to me fast.
Russ