These NVRs support Hikvision's free HiDDNS service, as well as DynDNS and No-IP which are commonly used DDNS offerings. I would suggest a Hikvision NVR if you're planning on using Hikvision cameras for optimal compatibility.
If you're planning on running 4x 4MP cameras, I'd steer clear of the DS-7604NI-E1-4P. It has been our experience that the NVR begins to struggle and can't handle the four cameras reliably if they're running at 4MP, with 12+ frames per second. The 7608 would be the one if that's the case.