People could be more helpful with more specifics to work with. What kind of bike do you have now? What do you like about it? What don't you like about it? What will your budget allow?

I think the best new bike in the $1100ish price range might be the Bianchi Volpe—it's not especially sexy, but it's an awfully comfortable and durable ride with a sensible spec, with only the tires and saddle standing out as obvious junk that need to be immediately replaced—but the differences between most bikes in that price range are quite minor.

If you're comfortable with it, you can get a lot of bike for that much money on Craigslist; even budgeting in money for a serious going-over by the LBS you'll come out well ahead, with lots of money for new lighting and baggage and other gizmos.