Arriving at a Bandwidth requirement is dynamic and it depends on how many files do you generate and plan share per day ? and the average file sizes.
If you have plan to generate large number of files, You can choose selected folders to replicate instead of the whole vault.
Just my two cents !
We have a similar with a remote office using a wireless WAN that gets 3Mb/s on a good day. There are a few issues we run into.
The bandwidth limit is very easy to deal with, just limit the replication, and schedule the replication for times when the bandwidth is highest. Enterprise seems to do a good job of using the bandwidth it has. The speed might leave something to be desired.
For us the bigger issue is latency. We find that even if all of the files are on the local archive server, when there is lots of activity going to the SQL problems can arise. Certain actions start failing, and users get strange errors. I don't have a solution for this but it is something to be aware of.