add instant messenger program to membership website

Hello, we are in the process of creating/finishing up on a membership website. We would like to add the option for members to have instant messenger as a service to communicate between members on the website within there profile... there are a few programs we have come across however we would like to hire someone who knows of a program that best suits our needs... Ultimately the program will allow unlimited users, and the admin (website owner) ability to turn on/off for each member....im program will be private label so our company name or logo is used and have a desktop feature so it can be added to members desktop screen....example of software/program we have in mind is @ www.123flashchat.com... Please provide us with the cost of a program/software and cost to install... We are also going to be doing a redesign for the homepage, so future work for those who are qualified.... Thanks so much for your time!!