do they sell canister filters at petco or petsmart?

You will still have to replace foams though, but you can cut your own
 
If you do go check out Petco/Petsmart you may have to ask an associate if they have any. There are a bunch of stores around mine where we can't have canister filters on the shelf because people will steal them. So...we have empty boxes or big empty spaces where they used to be. If you don't see any it won't hurt to ask :)
 
I've had an XP3 running for about 6 months. No problems at all. I have the foam pads that they provide in the bottom basket, a box of bio things in the middle basket (look like sprockets), and a fine polishing pad in the top basket. Works great for me. I rinse the bottom foam and top polishing pad once a month with tank water...no deteriation noted at all. I don't rinse the bio stuff in the middle basket. The fine polishing pad in the top basket seems to need to be replaced about every 2-3 months...it gets pretty nasty, and doesn't rinse clean after 2-3 months.
I do keep an extra pad that fits the filter in my other tank in the middle basket with the bio media in case I ever need to completely clean my other tank filter.
 
AquariaCentral.com