I am going to install either a IP-PBX System or a combination VOIP with 4-line telephone system in a new business of mine. My husband (who is a builder) is going to be doing the inside wiring but I don't know what kind of wiring to buy; Do I purchase cat5 for the internet and cat3 for the telephone or go cat5 all the way...or something different? Clear voice and data speeds are both crucial. Can somebody please (in laymans terms) help me with this information? Thanks!