DA has a lot of options, canvas prints/fine art/etc. Even printing on mousepads and mugs, which you can get done at CafePress... But Cafe Press looks lousy to me. I am unsure of DA quality, I bought a print of my art for a friend. He assured me it was beautiful, but I don't know how well he knows quality printing.
I used to work for Ritz camera and was very familiar with different prints and such (though I have no experience with canvas prints, etc). I printed quite a bit of artwork via the regular photo lab.
If you want to do something like that, shop around different locations of local photo labs in your area. I recommend Fujifilm labs like Walgreens uses. Kodak has thinner paper and really skimps on quality for profit margins. Also, look into your local darkroom processing labs and print shops.
A lot of people I've know use Vistaprints. At least for things like business cards and postcards. Unsure of anything like art prints. A friend uses them and sent me one of her postcards. The DPI print out looked pretty good and cardstock was nice and thick.
Guess, my information is kind of useless for buying prints from DA. I kinda went off subject there, I'm tired. I ramble.
Suggestion, purchase a small inexpensive print, 4x6. If you are satisfied with the quality, go ahead and buy the big one. If you feel that it is of poor quality, contact the artist, let them know their print didn't come out well and see if they use another service.
I haven't been able to afford any prints yet, but will look into printing elsewhere, as I feel DA prints are costly to the artist. their cut is too large of a percentage... ;P