I'm looking into purchasing a pre-built Media Center PC (Alienware, for now).  I know how to build PC's, but I'd rather not build this, as I'm not all that familiar with the best components.

What I'm looking to do is be able to record shows (HD and Standard) and rip and store my DVD's, music and pictures.  In the future, I'd like to be able to stream all this content to any TV in my home, but I'm going to start off small to begin with.

Is there anything else I would need?  Here's the setup I'm looking at from Alienware:

H18 Recording Space: Store 480 movies or 2000 TV shows or 960 hours - RAID 0 Configuration with High Performance Data Syncing (2TB Maximum Storage)
H18 TV Tuners: 1080p High Definition Video with Blu-ray Disc High Definition Burner - Record 2 TV shows at once (1 Analog & 1 HD/Digital Tuner)
H18 HDMI Cables: HDMI Cable – one easy cable for all your video and audio
H18 5.1 Channel Surround Sound: Hangar18 Standard Sound Output
H18 SPDIF Cables: Digital Coaxial Cable – Approximately 6 Feet
H18 SPDIF Cables: Digital Optical Cable (Toslink) – Approximately 6 Feet
H18 Performance: 40% Faster than Standard (AMD Athlon 64 X2 4200+ and 4GB† of Memory)
H18 Wireless Capability: Wirelessly connect and share all your content – (802.11 b/g Internal Wireless)
H18 Remote Control: Gyration Remote – No need for a mouse
H18 Remote Control: Logitech® Harmony® One Universal Remote - More Info
H18 WebGuide: WebGuide - More Info
H18 Gigabit Ethernet: Onboard Gigabit Ethernet – Quick, wired, internet connection
H18 Accessory Cables: RCA (Red, Yellow, White) analog A/V connectors
H18 Accessory Cables: 1.8M Ethernet cable M to M
H18 Accessory Cables: Communicate with your Cable or Satellite Box – Two IR Blaster cables
H18 Accessory Cables: S-Video Cable – Approximately 6 Feet
H18 Keyboard: Logitech® diNovo Edge Wireless Keyboard - More Info

Also, if I have no other PC in the house, would I be able to browse the internet and watch TV at the same time?

If you want to record encrypted HD and SD digital channels, which in most areas is everything but your local stations, you'll have to get a certified CableCARD system with the ATI Digital Cable Tuners and get CableCARDs from your cable provider. From what I can tell the Hangar18 is not CableCARD ready. Dell has the XPS 420, which many of us have.

If your box isn't gonna be a dedicated media center PC the recommendation is to make it a quad-core, otherwise dual-core is fine.

Hmm.  If my provider doesn't have CableCARDs (I know this was an issue when the Series3 came out), would I be able to use the HD receiver instead and just hook that up to the PC?

I'm looking at the XPS 420 now and I really like it.  It's a lot more customizable than the Alienware stuff.

I also still haven't been able to find an answer to the web browsing and watching TV at the same time.  If I were to get a seperate monitor, would that work?

Every cable provider is required by the FCC to provide CableCARDs. If they refuse to provide it to you, report them to the FCC.

Yes, you can browse and watch TV at the same time. Your TV is just like a monitor. Windows Media Center runs as a full screen application, but you can switch to windowed mode and have access to your full desktop.

Forgot to answer your other question. No, you can't hook up the HD receiver to your PC. There are hacks to do it, which involves modifying the HD box. I wouldn't go down that path.