How different between B&W 804s & B&W 805s????

I'm currently using a pair 805s and having a good chance upgrading to B&W 804s. I know that floorstanding speakers always better than the bookshelf but how different??? I'm also saving some money 4 my new amp(my target is Mcintosh 6900 or 2275), so, shoud i upgrade this speakers or saving that money for my future amp????