I would like to recommend an MSI notebook, theyr not overly expensive, use good components, have good warrenty, and I have excellent experience with them myself. For $800, you can get the CX61.
Thats an i7 processor, 6gb of ram, 750gb storage, and a standalone Nvidia 645M graphics card, which will nicely speed up your gpu-accelerated processes.
link:
http://www.newegg.com/Product/Product.aspx?Item=N82E16834152377
That said, almost all laptops in this price range use the horrible, and outdated 5400rpm hard drives. The MSI does the same. I can't really recommend anything using these drives for editing, as faster drives would do wonders for your editing experience. Manufacturers try to market their notebooks with lots of ram (even though you are often off with less but faster ram), lots of disk space (even though you are often better off with a smaller but faster drive), etc, etc.
So I would strongly recommend having the hard drive upgraded after you buy it. Your local computer store can swap out that slow hard drive with a solid state drive. SSD's have read/write speeds that far exceed traditional HDD's, and come alot closer to the speeds of RAM memory, and improving your entire experience.
The good thing is, you can always do that after you buy the notebook. The MSI will give you the most bang for buck (as far as i know) If editing goes smoothly then, thats good, don't change a thing.
If you still feel you want to improve, you know that the hard drive is the bottleneck.
P.S. Sweetie is right, if it doesn't absolutely have to be a notebook, you'll get even better bang for buck buying a desktop.
