Used.
I would also encourage you to consider a used SLR, especially because it sounds like you're exploring the hobby and not 100% committed. You could try ebay or craigslist, or talk to your instructor about good sources of used equipment.
There are lots of DSLRs that are 1-3 years old that would be packed with features and produce high-quality images, but could be had much cheaper than any new model.
Also, if you already have (autofocus) lenses, I'd suggest you get a body from the same manufacturer.
Good luck and have fun!