If you want to have someone totally build it for you, these sort of things are half decent. And of course if you have issues I'm sure they cover that (check)
I might be wrong, but Aria probably do something similar.
Base your fps on somewhere where there are no other players, or offline. For each player or mob that enters you line of sight (360 degrees), a %age of fps will be impacted no matter if you have a £3000 mega computer or an el-cheapo £200 hand-me-down. Each other player/mob requires fetching information from the db on the server. Less so for a mob, but it's still an impact. The better the servers/isps get, the smaller the %age. (it is minute - but factor 1000 players on your screen and suddenly it's a reality)
Memory helps this, but the game is only 32bit, so can't see beyond 4g address space.
Only way to beat that is to visit the server farm, patch directly in, and prioritize your port