I don't mean http Load Balancer but load balanced external app (lsapi). Of course data gotta be shared with that external app - by NAS for example.
That way - php can be compiled on other machine/s - thus giving more flexibility and scalability - thats what we have in plan.
It's just not a best idea to keep all of that stuff including mysql (and probably mail?) on same machine while you mentioned 800 accounts.