so, let me get this right...you want to upgrade ALL of your 6 internal speakers (not including the factory sub), plus an amp and sub to plop in the trunk? If you're looking for decent quality to upgrade all of that, then I don't think that's a large enough budget.
Honestly, I'd go with just the amp/sub in the trunk at first and get some good quality components and then save up a bit more and get a good quality upgrade of your internals. You can easily do it all without upgrading your head unit, it's just that an aftermarket HU will give you more options/quality, but that can be resolved with a more in-depth aftermarket solution if you truly want to go that route.
Start off with the amp/sub combo in the trunk, of which there's a couple articles on these forums already. Then when you have a bit more piece together a proper solution for the internals. Good luck
