Can anyone state what kind of speed would be suitable for 40 max users at a time? What if 512K is indeed suitable?
What kind of data is sent back from the reports, how much traffic does each one take? is it just text or are there any headers/graphics included in the report?
If you really do mean 40 open connections all sending data at the same time, then 512kbit is not going to be suffice for almost anything, without your users noticing how slow it is.