I saw that 6 gallon bookshelf tank at my Petco the other day too. It looked really nice and came with everything I think. I believe the price was around $45.
Shemetz, I agree, a 5 gallon tank would be best. I had Tofu in a 2 gallon bowl that was unfiltered and it was a pain because I was always having to do complete water changes, and he just seemed unhappy.
I went to Walmart and picked up a 5 gallon tank set that came with a 5 gallon glass tank, the hood, light, and filter. And it was only $29.98 for the setup. All I needed to buy extra was the heater.