Enhancing NT Terminal Server 4.0

I am using Windows NT 4 Terminal server across WAN, however i’m looking for a way to enhance the performance in order to improve the performance of some of my business and financial applications which run across WAN on this terminalserver. Citrix had been mentioned to me but I don’t know how this will help, any idea about how it works?, Or you know any other product that could achieve the same thing with proven record ?