I agree with Bert that the client-server best optimizes your resources. Small Biz Server should fit the bill for most practices using AC. However, as I have watched this thread go to 6 pages now, about primarily one thing: slow performance.
The issue as I see it is in the architecture. Until the architecture is changed, you will keep throwing bigger and bigger hardware to try to solve what is essentially an architecture issue.
It would be interesting from a technical perspective to know how much the mdb file grows with each day of work. Remember you have to pull the entire file to your client every time you use it. So if the file growth is significant, it may be a matter of months before your new super-duper server starts to slowdown.
