I have seen quite a few towers with speaker pods on the exterior sides of the tower that looked really good, especially when they were staggered on a forward leaning tower.
A lone set over the top of the tower can look like bug eyes and could use a couple of whip antennas up there to complete the theme.
Certainly moving the speakers higher helps out the occupants in the rear of the cockpit.
Moving the speakers to the interior vertical portion of the tower usually means mounting them lower which is considerably harder on the rear occupants.
If you have a V-drive then moving the speakers as far outside as possible can help clear a path down the middle. If you have a direct drive then moving the speakers to the center helps avoid the traffic pattern.
Moving the speakers to the tower front-to-rear connecting bars of lesser diameter can net you an inch or so of reduced hang height, or more if the bar is flat so that you can direct mount without the use of the collars.

David