I would say YES to that... s the lvl 75-80 bosses only give 80-90 silver and you need 2800 total then you want as high boss as possible... as has been said the ?-4 and ?-8 maps also have a small chance for a rare boss with 500 silver a tap and 500 discovery or they did on the DMM title.

EDIT: That might have just been ?-8 tho... my memory is fuzzy on that point.