Sony's VAIO RB series features two configurable systems and a cluster of feature-set boxes, some bundled with monitors, others without. This series is notable because all of the systems come in midtower desktop cases and many can be powered by Windows Media Center 2005 Edition. They won't integrate seamlessly into your living room like machines with component-style cases, but with prices ranging from $590 for the VAIO RB49C (with Media Center added) to the $2,030 VAIO RB38G with a 19-inch LCD, the cost is low enough that almost anyone looking for a full-featured home-theater PC can get their hands on one.
You wouldn't want a VAIO RB series for gaming. The best video card you can get is the ATI Radeon 300, a budget card designed for only passable 3D graphics. And you'll need to look to the higher-end VAIO RA series for media-friendly dual-core CPUs. The VAIO RB series' 64-bit Intel processor is generally fast enough for most basic media-consumption tasks, though, so as long as you don't intend to get involved in a lot of content creation, the VAIO RB series is a competent, capable home-theater PC.