it's an awesome unit, I have the "slightly" upgraded model (newer year, basically..)

if you're going to get the navigation, i recommend buying it refurbished / used / wherever the cheapest is..

there really is no point in buying it used, there's a brain, antenna, and wiring harness.. nothing really to be broken.. and you can save tons of $$$$

(example: Kenwood KNA-G510 Add-On GPS Navigation Module COMPLETE - eBay (item 380179894996 end time Nov-30-09 10:54:08 PST)) it's where i bought mine (no affilation to seller)

crutchfield has it for Kenwood KNA-G510 Add-on navigation system at Crutchfield.com.. $600.. yikes!