Unfortunately, the levers are the most expensive part of the group. If you want better levers, it's often a good idea to just buy a bike that already has them.

A Sora bike will be an 8-speed bike, of course; all of Shimano's other road groups are 9-speed. If you upgrade the levers, you'll probably end up wanting to upgrade the cassette as well.

Now your $600 Aurora (which is a very nice bike for the money) is a $750 bike, or more. So what would you look at in that price range? The Fuji Touring, for example, like the Aurora is a cro-mo bike with a road triple/MTB rear combo, but it already has a 9-speed setup (Tiagra shifters) and you should be able to get one for under $750. Or the Bianchi Volpe, which is a little more money but is pretty much the original of which the Aurora is a copy.

On the other hand, I have a bike with Sora levers (and one with 105 and one with Ultegra) and the Sora levers aren't really an issue. They work just fine, and they're just as comfortable under my hands as the others. (99% of the time they're just hand rests anyway.) The Aurora is otherwise a fine bike that's well-equipped for the price; maybe you should give the Sora levers a chance. You can always replace them after they wear out.

RichC