i used to do the independant screen and independat dvd HU.....it was fun, your placement of the HU like that is pretty **** cool, i think thats way better than making the hole a double dinand haveing one on top of the other like i used to....looks very very custom shop work with that placement (fools the noobix)...
cool thing isdown the line you could always sell the alpine and upgrade to advd indash, and have just the rear video preouts to the pioneer and have nesource on one screen and another source on the other screen (Ex dvd/radio on one and an N64/playstation on the other)...im miss haveing goldeneye in my old maxima....