Upgrading speakers, etc in 06 H3

Hey guys..  I am looking at upgrading the speakers in my 2006 H3.  The problem is, I LOVE the look of the stock head unit, the way everything is brushed metal..  I feel getting a touch screen or a different unit would ruin the look that I have grown to love so much.
 
In my last car I had an Alpine touch screen DVD player deal with a full speaker, amp, changer update done..  which I loved.  But, I am really on the fence about getting the same thing done to the Hummer.
 
Also, I replaced the XM brain with the GM Sirius one so I can continue enjoying satalite radio.
 
SO..  my question...  has anyone just upgraded the speakers without doing the head unit?  If so, what brand, type, etc will sound good using the head unit's power?  Or is the head unit capable to running an amp as well? 
 
When it comes to car audio I am pretty ignorant, so any help would be appreciated!
 
Dave

I changed my stock door speakers for JBL's they sound much better than they factory made in mexico speakers........It wasn't to bad just had to drill a few small holes and I also added a bunch of dyna mat