I'm looking for a decent sound system for mazda 3. What brand should I go for? Is SoundStream any good? I plan to only get speakers because my head unit is built in and I don't plan to change that at the moment.

My budget is $1000 dollars and I'm in australia. So it doesnt make sense to quote my budget since i'm australia. FYI, I just need a decent system without the need to be too high-end. there are few things i want to know:

is soundstream anygood?
My car has 4 speakers in total, 2 at the front doors, 2 at the rear doors. So what configuration should i use?