so anyone know more or less how much more the DVR box will cost me?
Assuming you already pay for some form of digital service, the incremental cost should be approximately $10-12/month. No one with digital service should be without the HDTV DVR. It's a $600 box that will record two different SD or HD channels at the same time at 100% original quality, while simultaneously allowing you to watch a third, previously recorded program. Did I mention skipping commercials to watch all your 1-hour shows in 40-42 minutes?
If you have analog service (i.e. no digital service), then the decision isn't quite so easy, because then you have to pay for the DVR plus
some level of digital service. The cost of digital service varies by region.
Personally, I would never be without a HDTV DVR, because the value I put on watching every 1-hr program in ~40 minutes, without commercials, far exceeds the price that my provider (FiOS) charges.