Look for a portable MP3/Ipod system that provides great sound and a remote. Re-chargeable is a plus.
I have a sony stereo system installed and in the end it was a waste of money as it gets used as an Ipod player 99.9999% of the time. I also end up dragging my portable/rechargeable Ipod stereo system with me at times because it is just so easy.
IMHO it will boil down to your electrical system. Can you recharge the Bose portable Ipod player? If so, go with that. If not, look for something quality that will run off 12 volts.
Being able to move your system to the beach, marina pool, picnic on a little island, etc, etc, would be a huge bonus.