Right now, there's no contest between AMD and Intel - Intel's Core 2 Duo processors far outperform what's on the AMD market. That may change, but this is speaking for right now.
A couple of things I noticed from your build:
- your power supply is a little bit underpowered for that build. You really want to go with at least 500W for a Dual or Quad core, especially with an 8-series video card. I would even go with 600W, in case you ever want to add or upgrade components. Your PSU is really important, you shouldn't skimp here.
- Are you planning to use Vista or XP?
- The 8600GT is like the mid-range card of the 8-series. You probably will get so-so results with maxed settings on the brand-new games, but you'll get excellent results with current games. If you have a widescreen or high-res monitor, you may want to bump this up if you are going to be playing games like Crysis, etc. at high settings.
- Also, I would consider going the EVGA route for a video card. They come pre-OC'd and are eligible for the upgrade program. Meaning if you decide in a month you need a higher end card, they let you trade it in for a different model, and credit you the cost. Really nice and helpful.
- I always preach the more RAM, the better, though right now few things require more than 2-3gigs of RAM. If you have the money, by all means do 4gigs...but know that 32-bit OS's will not recognize all 4 gigs..
- I second PG's suggestion of a new case. I've had awesome success with Coolermaster Centurion cases. They're like $45 on newegg, very much worth it.
Also, for laptops, the Alienware models are not a great choice for the $1k and under budget. Clevo and Sager are boutique brands that make nice, well-rated gaming laptops for a great price. They're highly respected by the gaming set.
If you're going to look for retail laptops, make sure it has a dedicated video card, a lot of consumer laptops come with integrated graphics.