If you're serious about gaming (graphics-intensive AAA titles), you'll need a quad-core CPU.
If your game design/3D design work schedule involves complex rendering and/or CAD projects, you'll need a quad-core CPU.
It is going to be next to impossible to find a $1,000 laptop that will meet those basic requirements, unless you're willing to go refurbished.
On the other hand, if the answer to the implied questions above was 'no', then you'd be perfectly OK with a capable dual-core CPU. Standard benefits include better battery life and less risk of overheating. And $1,000 will suddenly open up a very large field of candidates.