From my experience I would say that for a 10 mile each way commute, and at your price point you might want to also consider a good quality used touring or Cyclocross bike. I've found that more upright flat bar bikes are great for short distances, but wind resistances becomes a real issue for longer commutes. Obviously it may be harder to source one, but you could probably pick up something like a used Novara Randonee, Jamis Aurora or Bianchi Volpe in your price range.

Also, if you are really interested in getting an internally geared bike, bikesdirect have this:

http://bikesdirect.com/products/mercier/kilott_wt5.htm

not sure what I think of buying a bike without first test riding it, but some people have mentioned it's a pretty good ride.