I'd look at the Jamis Exile for steel. I know it is MSRP for $1,100 but it is tough to find good steel complete bikes for any less.
For aluminum I would suggest riding bike in your price range at the LBS. Just about all the companies have something to fit your bill and all pretty much quality at the $800 -1,000 price point.
A couple of specifics; Specialized Rockhopper line
Kona caldera, cinder cone
Anyway, good luck in your search.