Have you thought about just modifying the handlebar and stem combo on your current bike? Take a look at the Nitto Moustache handlebar. You can find them at Rivendell's website or Harris Cyclery. If your current bike is great except for the drop bars, these will give you more hand positions than a flat bar and will be compatible with your road brake/shift levers so you don't have to throw everything out and start over.

One thing to keep in mind is you may need a shorter extension, higher-rise stem to make this handlebar work. That will put you back and more upright to take the stress off your shoulder. Also, if you are more upright, you may need a different saddle. But still, replacing handlebar, stem and saddle would be more cost effective than a new bike.

Not that I'm trying to disuade anyone from a new bike. New bikes are always great, but if you like your current bike and don't know what you really want for the next bike, the less expensive fix may be the place to start.