Hi John,
I think you have a number of options open to you. I own the Swaro HD65 with zoom and at 60x the zoom is still sharp but it is does darken sonewhat. Still I would rather have the option of zooming to 60x than only 48x. In the smaller scopes I wonder if you have ruled out the Zeiss, zooms to 45x and the Kowa 660 series, zooms to 60x and if so why.
Regarding clarity on the Leica 77 with zoom if you look at the review on Alulu you will find Kimmo had the same "problem". It would be interesting to try your current scope against the Swaro 65HD both at 60x. You may also have an older Leica zoom, I think they were improved at some point, though whether they are in the Swaro/Zeiss class is debateable. Although I'm not quite sure what you mean specifically by clarity if you want the best image quality you would be better going for an 80mm scope eg the Swaro which is the lightest of the top makes, see the Alulu reviews which also make the case for larger scopes. I don't know what tripod you are using but you may be able to make weight savings here too. Alulu reviews here
http://www.alula.fi/GB/index.htm