i purchased a 2003 touring with bose but no nav therefore i am considering purchasing a monitor maybe the fernheit t7000 .... my idea is to run one video wire coming from the monitor output under one of the seats then somehow eliminate my cassette player if there is no other input(since it is a media source that outputs audio)and splice those wiring to a new source(A/V switcher which is going to be located underneath the seat with the dvd player and nav box as)in order for this to work the way i want it to i was thinking of the a/v switcher has to operate through a voltage signal (whichever on works)when the dvd/nav powers up that specific media will both display video and audio now to control the power on the sources(dvd/nav) i wanted to add a relay on the power which will be controled by the third empty switch which is located on the center console with the seat heaters ....center being off then one nav and the other dvd .... therefore this is what i want it to do and i want to know if my idea is possible ???

when i press cassette it will accept audio fromt he a/v switcher the monitor will always be on with the radio and when i switch the switch to either source it will power and transmit audio video ??

p.s if anyone knows where i can by the exact a/v switcher please let me know