I've a few services running and I do not wish to use dmz as it creates security issues, I'd rather have it natted behind a firewall.
What do you mean by DMZ? SoHo routers refer to unconditional port forwarding to a LAN machine as a DMZ. In more advanced networks DMZ refers to a third network other than WAN and LAN, where hosts run services accessible to the Internet at large. Running this in a different network further protects the LAN network: hosts in the DMZ are exposed to the Internet and may be under attach. If breached this doesn't gain the attached access to the LAN network as a firewall doesn't permit DMZ hosts to establish new connections to the LAN. A real DMZ doesn't preclude NAT in any way, and is a LOT more secure than port forwarding to the internal network.
Sorry, I should have been more specific. Its a pc (Win 7) my son has that We use as the household media server box, I've sabnzb, utorrent, sickbeard and couchpotato running on my own user account. My son also has a user account on the same box and uses it as his pc, therefore I'd rather not dmz it as it leaves the pc exposed with his admin account in the dmz.
I have many browser login pages and apps on my phone that I'd like to be able to connect to the box both on lan and when out and about with the same dyndns hostname without having to use the local ip when on lan