Now that we're playing height and frame size...
I'm 5'8", 31.5" inseam - so a shortish torso, I think. Certainly longer legs than the OP (Unless his pants don't fit.

.) I was on the cusp between a 17" and a 19" Hardrock when I bought mine in '07, and their sizing was still the same as the Rockhopper.
Generally, people with longer torsos get larger frames for their height, although, especially on an entry-level bike, there can be problems like too large a head tube making it difficult to get the handlebars low enough.
Other things to think about are that the relationship between your weight and power output will effect your riding position, as will your flexibility. Elite riders aren't riding low and long because they're trying to stay out of the wind - it's to counterbalance the power they're putting into the crank. AM and DH riders like a shorter reach because it's easier to get behind the saddle on a descent, and a shorter stem because it's easier not to endo or dive the front end.
Luckily, our bodies are pretty good measuring sticks for bike sizing. It's good if you can do enough of a test ride to try riding at a high power output, which may reveal too small a frame, and popping some wheelies and riding down some stairs, which may reveal too big a frame. Of course, demoing on dirt would be ideal, but it's rare to get that opportunity.