Upgrading a factory audio system offers better sound but also some universal inputs and outputs that aren't typically possible on a factory setup. While there are kits available that allow the addition of back up cameras and other auxiliary accessories to a factory deck, those modules are generally expensive and complicated.
This Nissan Pathfinder owner went with the Pioneer MVH-200EX which offers excellent sound processing and a nice 6.2" WVGA display. Surprisingly, this fairly large vehicle did not come equipped with a factory back up camera, so we took advantage of the Pioneer's RCA input to add a camera to make parking much easier.
We feel that a back up camera is a must have for a vehicle of this size. With the tall ride height, it's possible that small children may walk or stand behind the vehicle, completely out of the driver's line of sight. Back up cams come in all sorts of styles but we went with a license plate bracket style unit for this vehicle. This type of camera is easy to perfectly center, making for easier stall parking.