Stay away from the iCult. You get massively less for your money, for a grand you will be getting about the same as a $600 PC. And if you ever have to have service done, or replace something like a power cord, you will pay with your first born for it.
Like Thor said, get an i5 or i7 cor the CPU. AMD makes crap for mobile CPUs, and the other CPUs from Intel are garbage really. You wouldn't be happy.
At least 4gigs of RAM, there is no such thing as too much.
Get Windows 7 if you can. Do not get Windows 8.
If you are going to play any games on it, make sure you have an nVidia video card, and not just the integrated Intel chip. Hell, if you are really going to use it for games, think about shopping something like an Alienware that will be built for it.
You might think about brand by how their customer service ranks. There are precious little differences in most of the hardware between brands.