The only real things you need to be sure of are the voltage (19V in this case, I gather), the polarity (assuming that it is DC power we are talking about), and that the PSU is able to continuously provide sufficient current for the DVR (or any device being powered). How high the PSU's rated current output is doesn't matter as long as it is equal to or greater than the current required by the DVR.
Also, be sure to make sure you're comparing the same 'type' of output power rating... i.e. don't be comparing RMS/continuous figures with a Peak/Max figure

It is unlikely that you would be buying/using an unsuitable type of PSU, but it is worth mentioning that there are various technologies that are used to rectify DC power from your house's AC mains power. Just be sure that the PSU you intend to use is of a suitable type - be it a transformer with bridge rectifiers, a regulating circuit, a filtered switch PSU, etc.



Random FYIs regarding posts above:
Whether or not it would blow/trip the AC Mains fuse/CB would depend entirely on the build of the PSU. A fuse will blow for the same reason that a CB will trip and both components serve the exact same purpose, so whether it blows a fuse or trips a CB is somewhat irrelevant.

Just for the sake of mentioning it, CBs do tend to trip 'easier' than a fuse will blow... i.e. CBs have less 'tolerance' for surges of excess current when compared with a fuse of equivalent power/current rating.

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