Max number of IPSec connections??

I'm planning to use IPSec on a W2K3 Server that is hosting a file share and
will have somewhere near 900+ users connecting. And the policy I'm going to
set up will only state to encrypt on port 445.

The question is-Is there a limit to the number of IPSec connections that I
can have before I see any performance issues on network bandwith or on the
server? I'm sure both may very depending on network speed and the size of
the server, but was hoping for a general rule (like not recommended for more
than 1000 clients) or an article stating any limitations.

Thanks,

Jeremy