+1 with GsEclipse, but it all depends on Bose. My mom has Bose in her Maxima, and the highs completely suck, theyre watery as shit. I would much rather have Type S components, even powered off a head unit, over her Bose. Although my opinion is that Bose car audio sucks in general (Maxima bose head units have a technical service bulletin aka recall, etc)...I have heard decent Bose setups.

The other thing is that you might as well get a new head unit if you are going to replace the speakers because most likely your bose amp runs at 1 ohm and won't work with your speakers. If I were you, I would pick up a head unit with a good internal amp, pioneer or alpine prolly, and a set of Type S coaxials on ebay which are 50 bucks, and call it a day. Type S is about all you can get away with when using the head unit to power it though, but yes they will sound much better off an aftermarket amp.

Cliff Notes: I think Bose car audio sucks, but I have heard good Bose. It depends on your car. If it were me Id get a new head unit and Type S rears and call it a day.

Hope this helps

Kevin