Shotguns are ideal for home defense.
Remington 870 Express is inexpensive and reliable as hell. Load it up with #4 buckshot and call it a night. Only problem is the finish on the Express. Very prone to rust, but the less expensive Mossbergs are the same. If you feel like laying down some more cash, the 870 Marine Magnum is the way to go. I'd love one of these babies! Higher quality all around, but probably $600 or $700.
If your not looking at concealed carry, the Glock 22 or the smaller 23 are the way to go. Both are .40 S&W cartridges. They run about $500 brand new. I have the 27, which is the same, just smaller for carrying.
If you're more of a revolver fan, your quest begins and ends with the Smith and Wesson 686. Bad ass. Fires .38 and .357 magnum rounds. They come with varying barrel lengths and they are not cheap. At least $700.
As for best prices, I've gone to a few stores in the Pittsburgh area, but my best advice would be to shop online for the model you want and get a price in mind. I hear a lot of stores negotiate.