well to be honest the flexibility you're allowed with your kit lens is actually very good for only one lens. I would learn to master that lens before branching off. Long zoom lenses are either good and expensive or bad and cheap, its just a matter of varying degrees of price. Generally anything longer than 70mm is a zoom and costs less than 600-800 bucks should probably be avoided
after you feel like you've graduated from the kit
either
http://www.adorama.com/ISO2470.html
or
http://www.adorama.com/ISO247028VSZ.html
are excellent all around lenses
for longer zooms any of the family of 70-200mm of lenses from the major OEMS (in your case sony) are excellent choices, albeit expensive. they generally start around 13-1500 bucks for f/4 + image stabilization and go to around 2.3-2.5k for stabilized f/2.8 zooms.
For any zoom if you intend to do low light anything it is worth saving for the f/2.8 version.