Alienware has a nice looking but very expensive new HTPC system called Hangar 18.
The system is powered by a dual-core AMD Athlon 64 X2 processor and you can choose between NVIDIA graphics cards with 720p or 1080p HDMI out. The operating system is Windows Vista and the storage capacity ranges from 250GB to 2TB, depending on how much cash you're willing to pay for this machine.
Audio and video features:
5.1 channel surround sound Audio Amplifier
Analog Audio in
Optical Audio out
Analog Video Out
Dual TV Combo Tuners ( 1 analog, 1 High Definition )
Up to 4 TV Tuners ( 2 analog, 2 High Definition )
There's also a beautiful VFD display, a Gyration remote control, a slot-loading DVD burner, WiFi 802.11b/g support, 4 USB 2.0 ports, a FireWire port and a 4-in-1 memory card reader for SD, MS, MSPRO and MMC memory cards.
The Hangar 18 measures 4.2" x 18.4" x 15.55" (h x w x d) and weighs 18lbs. Prices start at $1,999 but that version doesn't support 1080p. Depending on all the options you want the price can more than double.
The back of the Hangar 18 also looks really good, Alienware did a superb job on the design of this system.