Three quick points to consider.
1. If you are replacing an existing system that has a high portal for the camera you can use the existing cable for a single camera system. All you need are two cable adapters to take RG cable to DIN cables. About $2 each.
2. With the "portal" mount the IR lights will create glare from reflecting from the plastic view port.
3. On a 7" monitor you will not see any significant increase in resolution for a CCD camera Vs a CMOS camera.
BTW, the 7" monitor in the Leviathan system is exactly the same unit as came with the $92 system.