I replaced a bunch of standard cameras w/ IR LEDs, as well as the DVR.  We switched from a propriatary Linux based DVR to a WInXP box running Nuuo.  The cameras were "OK", but the quality was just not great.  I look at security cams not only as a deterrent, but also as an evidence gathering tool.  If a crime is committed, and you just have a blurry face, the cameras were not worth installing in the first place.