Here are my choices...
eMachines T6420 - The eMachines T6420 delivers major bang for your buck, including a roomy 200GB hard drive and upgradability in a fixed-configuration retail box.
Mac Mini Core Duo - The littlest Apple receives a makeover that includes more than just the widely publicized move to Intel processors. The feature-rich dual-core Mac Mini Core Duo offers impressive specs for the price and includes a remote control and Front Row software, better multimedia ports for entertainment-room connections, and an improved ability to share media with other computers on your network.
iMac Core Duo - The iMac Core Duo is Apple's first desktop computer to result from the company's partnership with Intel. A visually stunning gift idea, the iMac Core Duo boasts cool features such as an integrated iSight camera, a remote control, and Front Row, Apple's Media Center-style software. If you use Photoshop or other nonnative apps, wait or look elsewhere; otherwise, Apple continues its trend of delivering better technology for the same price.
Velocity Micro's Raptor - Velocity Micro's Raptor line of gaming systems are proven performers, and the new Raptor 64 DualX is no exception. Driven by AMD's new dual-core Athlon 64 FX-60 processor and a pair of powerful GeForce graphics cards, this pricey ($5,395), overclocked system is built for speed.
Velocity Micro Gamer's Edge DualX - Velocity Micro Gamer's Edge DualX is a near-perfect gaming system that won't break the bank. Even with its lone graphics card, the Gamer's Edge DualX is a screamer, and there's room for a second card if you aspire to SLI in the future.
HP m7300 Media Center series - If you want to turn your den, home office, or dorm room into a home theater without making the move to an A/V-style form factor, the HP Pavilion Media Center m7300 series offers plenty of unique media-friendly features, including a LightScribe DVD burner and a slot for HP's Personal Media Drive.
Shuttle XPC P 2600g - SLI graphics in a small-form-factor PC? That's the minor miracle of Shuttle's XPC P 2600g. Just be prepared for sticker shock, thanks to high-end gear, including an Athlon FX-57 CPU and a pair of GeForce 7800 GT cards.
ThinkCentre A52 - Because nothing says holiday excess like, uh, a button-down business desktop, it's good that the Lenovo ThinkCentre A52 displays its IBM heritage with a smart design and strong business features. The system also includes several decidedly business-friendly security utilities that go above and beyond what we've seen in other recent small-business systems.
Creature Scylla S301 - Aptly named for the sea creature of Greek mythology, the Scylla S301 from Creature HTPC is the best high-end home-theater PC we've seen all year. It's a monster of a Media Center system with an equally monstrous $5,400 price tag. But for your money, you get more gear than that in many high-end systems, with bonuses that include a GeForce 7800 GTX video card and 1TB of hard drive space.
Apple Power Mac G5 dual 2.5GHz - The current Power Mac G5's industrial design--a gleaming, silent, almost spooky tower of power--will probably stand in museums long after Moore's Law sweeps away its components. And though we think Mac fans should give more consideration to Apple's tendency to overprice, underconfigure, and minimally support its desktops, including this top-of-the-line Apple Power Mac G7 dual 2.5GHz system, it's hard to argue that the company doesn't have a knack for melding form and function.