If your on a budget this is what I bought with a kitchen sink attachment
http://www.jlaquatics.com/product/vt...+-+100GPD.html total cost with attachment was $155 but I have seen these for sale for less than a $100.
I haven't had an issue with it and it doesn't take up a lot of room. You can also go to places like Canadian Springs as they sell water purification units and may even have some used ones for sale plus you can get your replacement filters through them as well.