-> You can always stick with a Mac and dual-boot with Windows via Bootcamp, but that would push you over your budget considerably.

-> You can usually find betters deals on AMD CPUs and corresponding motherboards, offering better bang for the buck if you're not ties to the Intel branding.

-> Asus is not the best motherboard manufacturer in the business, with an above-average failure rate and lower-end technical support. pairing the graphics card with a Gigabyte motherboard for a few extra bucks will give your computer greater longevity. Skip onboard graphics to shave the cost.

-> You can click here for a PSU wattage calculator/advisor.

-> Windows XP x64 was an entry attempt at the 64-bit market that failed miserably in terms of performance and driver support. Windows 7 offers better performance than Vista, making it my recommendation.