Audigy are pretty good cards, I've been using an Audigy one for a couple of years. Most of the upgrade on the ZS, from what I can tell, are based around music creation and recording. The gold plated plugs are slightly higher quality, but for games playing etc, the difference will be virtually un-noticeable (to be honest, gold-plated sockets are a bit of a turkey when dealing with digital audio anyway).
The Firewire can be used for Networking, I've used it to link two computers together so I could run multiple instances of Cubase, but unless you have other computers or Peripherals with firewire, it's pretty much a redundancy for you.
Basically, if it's a good games playing/mp3 listening card you are looking for, and you are determined to get an Audigy, the Value is fine. That said, CP is right, you might do better looking at cheaper cards, the Audigy supports 24Bit, 48Khz sound, which is great, except that there are no games or music available at that quality, it's basically designed for studio quality recording.
I use an Audiophile now (24 Bit, 96Khz), it's one hell of a card for recording, but, alas, has practically no Surround or EAX support whatsoever.