With its little side-flaps extended I can't help but see this pre-built MythTV PVR as some sort of Transformer, but sadly though its capabilities are broad I don't think they extend to being a robot in disguise. Still, you could have some pretty good times even without self-adhesive decals to position; $499 gets you an Intel Celeron 2.66GHz, 256MB of RAM, a GeForce 6200 graphics card, 80GB hard drive and 18x DVD burner, specs easily capable of running the Ubuntu OS together with one of the most well-respected PVR environments, MythTV.
Basically this is an unpack-and-plug-in solution to your media streaming/live TV pausing/scheduled recording needs. Yes, you could build your own Linux box and install MythTV, but this saves you all the effort, is cheaper than a Windows Media Centre and gives you access to a vast range of fan-programmed add-ons. Upgrade options include up to a terabyte of hard-drive space, multiple TV tuner cards and WiFi, with various models hitting price points up to $1099.
This would be a great way to cost-effectively get into PVR ownership - you could start with the basics and then add to it yourself as you can afford more. Definitely jumps to the top of my "must try" media centre list!