+1 to both previous posts. I actually have a laptop close to what Zargg suggests.
Be careful with the CPU since many I7's for laptops are dual-core. You have to look up the CPU model number (the -U ones are usually dual-core...used to be anyway).
Are you sure you want a laptop ? you can get a desktop for about the same price which gives more bang/buck, is upgradable, and is repairable. If you are not doing a mobile studio thing, I would go desktop.