Klaus answered the rest. I can speak to the audio upgrades.

I may or not be mistaken but I believe even the entry level speakers (not premium Volvo sound) are still Dynaudio. This company makes some pretty legit stuff.

If you are looking to upgrade you really won't benefit from dropping anything else in unless you choose to also install a new deck and then a power amp to drive the new speakers.

Example, people will go out and drop some cash on Boston Acoustics speakers all the way around and run them off the stock deck. Lets say speakers are 125w RMS and lets say your deck on a good day is dropping 22w....its like trying to tow a fifth wheel with a Geo... you'll try to get the loudness at the expense of maxing out the internal amps and it will sound like rubbish and you'll sulk in silence (trust me)

If you do it right and get a quality deck, new speakers and a complimenting 4 channel amp you'd be really impressed with the audio.

Car audio is greeted with many opinions from a lot of people. In my many years of wiring speakers and subs up I have to consistently say I am time and time again impressed with Alpine electronics (deck and amp) and then some Infinity or Boston Acoustics speakers. Do yourself a favor any steer away from any of those flashy no name brands and the likes from Sony, Kenwood, Dual, Jensen, etc. Alpine has always put out clean sound.

Steve

If you buy from Crutchfield all at once you'd be surprised what freebies you get from them (dash kits, wire harnesses, door adapters for speakers if needed...)