Unless you have a lot of money to spend on KTV, I would pass it by. The girls are pretty since they dress nice. It would cost you around 300rmb just to have a girl sit next to you and to talk to you. Then there is the additional fee of the room, the DJ plus the tip for the mamason and the servers.
The Chinese guys usually take their clients to KTV in order to impress them with the amount of money they are spending on their client. In China, the more money you spend on the client, the better chance you have in closing the deal. Then if you want to take the girl out, it would cost you additional 3-400 rmb for a short time, much higher for long time. Then you will find out that the girl is usually just a dead fish in bed since she already have gotten her money therefore no real reason to give better performance. The girls also know for the money you are paying, the chance of you coming back to her is about 0.
Just to give you a ball park price, for a party of 4 (not counting the girls) it will probably cost you around 3000rmb for 1 night, this is not including you guys taking the girls back to your room and assuming that you are not drinking like a fish. However fees of around 5000rmb is not uncommon.
Unless you really want to impress someone, I would just give KTV a pass.