Digital BW, The Print

I'm shooting a Mamiya 7ii w/ 6x7cm film and scan w/ a Microtek 120 MF 
scanner w/ Silverfast. The problem is when I scan at 4000 ppi optical 
at 16 bit my resulting files are 500+ MB, and that is w/o adjustment 
layers in the post processing stage which can be 1 gb+!  The quality 
BTW is usually better than my 5D Canon... I've tested downsampling to 
3200 and even 2400 ppi and I really can't see a difference which brings 
it down nearly half the file size.  I'm not even sure I can see a 
differnce when downsampling from 16 bit to 8 bit if I don't do much 
post processing. I'm just wondering what other folks do to keep there 
files sizes reasonable and still attain the highest quality...? 

Thanks in advance!
SteveB