Can I stream audio running OSX 10.6.8
You may want to review what Apple describes here: http://support.apple.com/kb/HT5404

Also, there is a decent tutorial here: http://computers.tutsplus.com/tutorials/five-ways-to-airplay-from-your-mac-to-your-television--mac-52157

But as you'll notice, it's more about the hardware.  You'll need an intel based Mac that was manufactured mid-2011 (early-2011 for MacBook Pro) or later.