I have the same color combo and its indeed rare. I just bought 20" replicas w/ Toyo Proxes, $2200 shipped cross-country from CA to MD, excellent quality and price. I bought my clear tails and sides from ebay, however, I chose not to change out the headlights, as you'll need to change out the entire headlight (unless you want to disassemble which is highly not recommended).

Can't help you on your sound system upgrade, as I just have the Premium w/ DSP and CD Changer. Just a word of caution, if you install an aftermarket setup, you'll lose steering wheel controls and onboard computer functions. I don't have NAV either (and regret that I didn't get it upfront) and went the portable GPS route, Garmin StreetPilot.

Enjoy your ride!!