Search for them in http://www.newegg.com or course //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif//content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif
Go with the Audigy 2 ZS Platinum Pro. I find that the Audigy 2 ZS PP and the Audigy 4 Pro are pretty much with the same thing but the Audigy 4 does have a little better DAC. Not sure if you'll heard a difference between then tho. Besides that, I find they are the same cards. Unless someone can prove me wrong about this.
Creative will be the easiest to work with. I have a Terratek card but it's more tuned for audio so you have to do some weird stuff to get games to work well with it. Another brand to look into is M-audio. The M-audio Revolution cards are supposed to be nice.