Sturmey-archer makes an 8-sped drum http://www.sturmey-archer.com/hubs_8spd_XRD8.php

I have a 7-speed nexus with roller brake (not really a drum), and I am not particularly thrilled with the brake performance. I am considering taking the brake off and going back to a rear caliper (already a caliper on the front).

Going to the taller tires will change your fork trail and change handling subtly. If it was really dialed in before, it will not feel quite right, but may not even be noticeable.