This system was built several years ago specifically to connect several cameras up at my home. It has 3 GB of memory a 1 TB hard drive and an Intel dual core processor. It uses a Hikvision 8 channel capture card running Unisight professional DVR software.
There is no option to run Linux on this particular system as the DVR software is only compatible with Windows. While I can run Windows 7, I choose to run Windows XP. Gigastrand will be developing a DVR software that will run in Linux and be very similar to the software that runs on my home DVR and current Gigastrand Security systems.
At one point this system was connected to a projector. With our cable box connected to the 2nd channel we could display the TV show we were watching plus 5 cameras around it. We can still do this however on a smaller screen it provides some reduction in enjoyment of our show. Additionally the signal is down converted from HD when watching an HD channel. So watching HD television through the DVR is sort of an academic exercise.
One benefit of running the TV through the DVR is that whatever is on the screen is recorded so we can monitor who is watching what on the television and even stream our live TV in low-quality over the Internet.
The DVR also has a couple of video outs so we can connect additional monitors as well as a Blu-ray burner so we can watch Blu-ray movies and burn Blu-ray discs. Also, being Windows we can watch Netflix or Hulu or whatever else we can watch on a PC.
I have loaded XBMC on this DVR however running the DVR software and running XBMC is quite a bit more than this particular system can handle at once. I am not certain if the systems will need to be separate systems or if a few upgrades will solve the issue. For now, the system is unlikely to change very much in the near future.