I'd say stereo speakers up until the Live, then hook them up to a 5.1 system with analog inputs if you can. The first live will only have front and rear speaker jacks for 4.0 though. To be honest I wouldn't bother with the live cards at all if you're using an Audigy 2zs. Just hook the older ones up to a good set of stereo speakers running through an AV switch box, and the Audigy through a 5.1 system.

What are you hoping to do with them? EAX positional audio, movies, games with surround encoding? That may determine how much effort you need to put into maintaining multichannel outs, or where to draw that line. (E.g., maybe 2-ch up to the Audigy, and use SPDIF switching from there? Or stay analog all the way through.)

I've got the same dilemma ahead of me. My thought -- because I'm a hardware hacker -- was to build an AV switcher with a 5.1 analog audio bus. I thought about taking advantage of digital audio where it was available, but TBH, analog is probably better in every way. For one, there are no issues with missing the first few samples of audio while waiting for the receiver to lock into the stream after a format change. (Although I'm not sure whether the Audigy changes its output clock very often, or maintains a set format at all times.) Second, the only way to do multichannel audio over SPDIF is to use compressed audio formats like Dolby Digital. Otherwise, you're limited to 2-ch stereo. AFAIK there's no high-bandwidth i2s exposed on any of those cards. So depending on the source, you may get better fidelity with the analog outputs.

I want to primarily use them for game play, but just want to make sure I have the right speaker setup for each card to get the best output from it....

Its the 2 Speaker, 2 Channel output for most of them and then once I hit the Live 5.1 / Audigy level I can start to lookin to using more features....

Unless you get the Dolby Digital pack for each card, your stuck with analogue for more then stereo and analogue x multiple card's = complicated mess so I put this on hold 2 years ago.
I'm not sure if the Daniel K drivers gets round this?

If you want to leave your receiver in surround mode, matrix decoding is usually fine for most applications (except music).

I do have a couple systems that have multiple cards in them, but in terms of output, I dont plan on having more than one card outputting sound at a time through the receiver.

Looks like for now its 2 channel for most....

I wasnt aware there were dobly digital packs for older sound cards? Is that right?

That's news to me. I thought some of the Audigy cards had DD licenses as part of the higher-end bundles. (The non-Value versions, e.g.) I only recently got hold of some Audigy / Audigy 2 cards though, and haven't done anything beyond install the software and play a few games over 2-ch line-out.