AliceSML79

my 07 300 touring has a boston acoustics am/fm/cassette/6cd/sat radio. only thing is i really want navigation. my question is should i go for a original mopar or would it be better to get the kenwood excelon dnn991hd that cost 1499.99 for just the head unit. then add a amp and replace stock speakers and ad a dual ported sub in trunk. i know id get way better features and sound, but is there anyway to keep the oem rear dvd entertainment system?

Thanks in Advance, Alice