Paul, I just purchased the cans and put the higher end Sony 6 1/2"'s in them and I have to admit they sound pretty good. Decent sound for low price. You probably want be able to hear them riding but they sound good in the boat.
Thanks guys. I won them on ebay for 177.50. I really didn't think that I would get them that cheap, but if they are not loud enough, I guess I can always put better speakers in the cans.