Looking to do serious audio upgrade - Sydney

[Oddman]

Hi all!

I finally have the means after some time to be able to upgrade my polo's sound system. Poor girl has had the stock audio absolutely pillaged as a result of me liking my music loud: left speaker gone, right tweeter gone, left tweeter and right speaker on its way out.

As a result, looking to replace (read: upgrade!!) the current system, meaning better splits, better tweeters, and a couple of 10" subs installed (preferably flat subs to save space). Ideally, I'd even like these on display in the back, but the the shallower the housings, the better (boot space isn't all that great!)

I'm not only looking for product suggestions but also installation suggestions - who's the best person to go to for this sort of work? Finally, may look at replacing head unit if it doesn't screw with the existing features.