Lots of choices there for sure...
I chose to go without racks and use bags,the advantage is that the entire system is lighter. I also knew that the larger bags/pannniers that I carried, theh more I would fill them... whether I needed to or not. I ordered bags from Relevate, and love the quality. Although the other side of that is that I waited very long for them with no communication from the company itself. There are a couple of other companies out there now as well... Cleavealand Mountainerring is another, so you could check out their site as well.
I did a review on the shop blog on the racks/panniers vs bags, maybe you'd want to check that out as well. http://chasecyclery.blogspot.com
If you're so inclined, there are also people sewing their own bags... so I could point you in that direction as well...
Good luck in your search!