I use a dvr made by IC Realtime, They make two different models Proview and Flexview. The pro is as good as i have ever seen but not the cheapest in the industry but worth every penny. They also have the Flex which you get alot of bang for your buck. They make it in 4-8-and 16 ch. It is very feature rich.
1.mpeg-4
2.built in Sony CD burner
3.up to 4 terr of internal storage with external raid- that will hold anther 12 drives
4.mouse interface
5.embedded Linux OS
You can see the specs on their site. Look under DVRS and then Flex series. They are very well priced for what you get and the service is top notch.
www.icrealtime.com