How many speakers is optimum? This is only when you have decided to go in for a multi channel surround sound system. The numbers of speakers to be decided depend largely on two important factors.
#1. How much is your budget? This is the first factor which decides on the optimum number of speakers. Lets say budget is not a problem for you then it depends on the second factor.
#2. How much space you have? The optimum numbers of speakers depend on the available room size. For a small size of room it would be a cabling mess if you go in for 10 speakers. Neither this much of sound output is required. If you have a smaller space and you don’t want to disturb your workspace with unnecessary cables the a 3 speaker standard unit will suffice. If you have a large room space then you can go in for than 5 speakers which will create a real surround sound experience. In such case you will need to conceal the cables well to avoid the mess. For better surround sound effect the speakers need to be placed separately with some distance among them. For a large room 10 speakers or even more than that can be said to be optimum.