GM navigation question for 08 tahoe (urgent)

Im about to buy a GM navigation but i wanted to know if i got the DVD compatible one and DONT have the rear dvd set up will the navigation radio still work without it? i dont see why it wouldnt.. pls let me know
Also i dont have bose speakers and i plan on getting rear seat entertainment in the future

GM Part # 15940103 is the part number

I think it would work, in fact you can watch movies on it (in park, unless you get a Lockpick or other interface). But I think you'll pay more for it and will miss the potential of the rear screen, or you should add some more screens that will feed from it. Don't see any problem with it though.