HELP WITH OPUS 500

Hi guys, i have just finished installing an opus 500 multiroom system in my house. and to be honest it is fantastic. i only need one more piece of kit to finish my system and that is a media server something with 2 zone preferably. before you guys start advising me to get a idly or a escent or even a imerge server. i want something a little bit more technical i would like to build a media server, i guessing that the above systems are nothing more then a pc with some fancy someware built in to the, this is where you guys come in, i want to build a pc system but with media server software built into it, i want to be able to hook the pc system up to me opus system using a XiVA protocol, any advice or links to software would be great thanks