The X-Gamer was released by Creative Labs to replace the now discontinued X-fi X-Music. If your still using the X-Music your not going to notice any difference between that card and the X-Gamer. -they all for all intents and purposes the same card.
There is not really that much of a difference between the two cards you linked to. The Fatality has X-Ram..etc. Basically though they will both sound the same, so people have stated.
Why can't you use the mic on your X-Music?
For voice communication programs...Many people use ventrilo and team speak. These require you to have a server to connect to, so they are usually used by clans/guilds. CSS has its own voice com system though.