Well...if this information is accurate, then I would not say you have too much of a problem at this point. However, if you have 2000 users as you say, I can tell you that an Ultra10 is probably a bit small, especially if you are doing logging and management on that box.

I would recommend going with a Nokia IP series appliance to run your FW gateway if you have the budget.

But as the saying goes...if it ain't broke, don't fix it...