I have 2 TF2 servers and they both use the same ranking, otherwise they are combined and not ranked individually. If a person jumps from say, tf2 2fort to goldrush, they'd want to retain their rank regardless of what tf2 server you them play on. Same with any other mod and Hlstatsx:ce works very well.
Now granted its a database monster; it's best to get a VPS or a dedicated IP(some shared hosts provide this as an option) I have the dedicated IP and my host is ok with the massive db and queries. But like mentioned above angrygaming is a great option too.