WHAT SPEAKERS DO I GET!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
What ever your budget will allow. As a resource, I like to use Crutchfiled to see what speakers will fit and then it is usually the best speakers that fit my budget.
MB Quartz, Canton, Memphis, Boston, etc are just a few names that make some top shelf separates. I'm sure there are other companies (Infinity, Kicker, Kenwood, JBL) that make separates, but I haven't done car audio in a while I'm not up on my knowledge.
also, visit your local car audio store (not circuit city or best buy) and see what they have/recommend. Also, speakers always sound different in the store than in a vehicle so see if you can listen to some already installed.
I would want to bet that the Bose speakers are paper or laminated paper. Its what they do in their homespeakers so I don't think their car stuff is any different.
You also may benefit from an aftermarket amplifier. It sounds complicated, but think about this...look at you headunit and imagine the amplifier built into it and it might put out 50wx4. Now look at a dedicated 4chan amp that does the same 50w and look how much bigger the amp is compared to the headunit. The amplifier should give you even better, cleaner sound than the headunit, but then a HU and new speakers my be all that is needed.
I know our '04 Bose sounds muddy and is bass heavy and isn't very crisp. The limited audio adjustments don't help either.