Hi,
just 2 pennies:

yes, compression on should be used in such configuration,
  and *sm client  is better suited for that than NTBackup.

do think in terms of restore, not in terms of backup backup: 
while you probbaly will succeed in backuops,
will you still be able to perfom good enough at restores, 
which are non-incremental by their very nature?

regards
Juraj Salak
salak.juraj AT eunet DOT at