+1 on what Badgercat says. Check out some steel frames. I've never ridden one, but there are plenty of people who love it on here. (Enough that I'm considering a few for my next bike!)

What I meant by a "nicer flat-bar road bike" (for that charity ride) was mostly in the components. I'm not what you'd call a weight weenie--all I care about is that I can pick up the bike and move it around without too much effort. Lower-grade components tend to require more tweaking, and on a long ride, that could be a problem. (Shifting is also nicer, I feel, with higher-grade components.) Since flat-bar bikes tend to use components that I'm not familiar with (no idea what Shimano's MTB components are!), I'll let someone else answer that.

(Badgercat, that Jamis Coda is pretty sweet!)