if you are developing a "social based" world where you can walk around and chat only then gamestudio might be the right choice for you.

dont get pro until you are comfortable with the c-multiplayer scripting and have something stable with 4 players running.

have a look at the multiplayer forum there are lots of threads around dealing with this. the thing is NOT a single game where more than 4 players play over the internet without any problems has been made with gamestudio. if there is someone please show me.

there are some smaller demos out there that proof that its indeed possible but its by far the hardest task to do with gamestudio.