I have the bose system - being replaced with Sony DD DVD, focal K power speakers with Focal amp, a JL 13 W5 sub and JL XD600/1 amp. Just still looking for a double din radio front panel to replace the Bose front panel.
Just the upgrade to a good 2 ohm speaker is already a big improvement over the bose speaker. In comparison the Bose speaker sounds muted. I did a test run with just the focal 2 ohms in, no other changes, and the difference is impressive. Of course no where near as impressive as driving the focals with a decent amp. I did it just to be able to compare...
As everyone says - the bose speakers really aren't very good.
If you are going to the trouble to change the speakers, rather do it properly - dynamat behind the speaker, dynamat the whole inner of the door, pull through decent wires, drive it with a decent amp, and change the head unit while you are about it. A decent system is going to set you back about $3000
But hey, we like to move it..