Hi All. can anyone give me the low-down on wether "Dual-Head" DVR's really exist, or are they a myth? I have been told that you can get low-cost DVR's without a HDD that allow you to record to DVD and watch what you are recording at the same time, by virtue of the fact that the have separate read and write 'heads' (not sure that heads is the right word - maybe I'm stuck back in VCR days there). If they do exist - what is a good model?