Well, Sots used Xfire as a advertisment tool. Many other games used it also (MageKnight, BF2142, etc). Xfire also supports a wide variety of RTS which includes Homeworld Series, and Nexus.

I'm sure it would be Sins' lost if Sins doesnt get supported by xfire.

Also the devs can probably work out an event with xfire and have the Xfire site and messenger post advertisements.

Xfire site: http://www.xfire.com/

Here's and example of an event:

Sots Dev Chat: http://www.xfire.com/cms/xf_sots_chat/