I found the XP2 on drfostersmith for $84.99, so I will probably go for that. But, I will check out Big Al's too. When I get the XP2, do I have to buy anything such as tubing separately for the filter?
no, everything is included, except for biomaterial media (eg ceramic rings).
it comes with foam pads, cotton, and their carbon ion exchange mix called biochem zorb, which is great IMO.