Sounds good Mitch. Best of luck.
If you're not competing in sound contests and what not at AutoSalon for example, there is no real reason to spend so much money on an audio system. I went through the usual 'sub, amp, 6x9's, etc' phase. When I look back on it, I prefer getting nice and clear sound over being fully hectic bro. I guess everyone has to go through it at one stage.
If what you've got can support it, then that's really all you'll need. And for small gains as psynthetic has mentioned, I don't think it'd be worth it. Besides, do you have any mates that are sound/audio engineers/technicians? No one will notice the difference between a $500 system and a $5,000 one. You'll be perfectly fine man.