The server is for 16 players, it's big enough for that but not too small. About the map, it isn't bad at all, it's probably one of the best RP maps out there. You have no idea how many good moments many other people including myself have had on that map and it'd suck to lose it. Plus most RP maps for GMod9 are kinda boring.
The ideal mix would be between city18 and oviscity - a map with a closed track to have car chases on and a lot of apartments so every player can have his own little private space