I am going to presume the OS installs are going to be Dos, Win95 and Win98. I like the idea of SB16, Awe32 and Awe64

Audigy 2 could be held more for a 2001-05 P3/P4/Athlon build, but should go okay with a K6-2

AWE32 and 486DX4100 would be rather period correct and high end, as would an AWE64 with a PMMX233

GUS Max has Win95 driver issues which keeps it out of the DirectX age, so that's probably also fine for the 486 if you're sticking more to DOS/Win3x or just early 95. The lack of OPL and the differing game compatibility is an acquired taste however (not too many cared to hardware mix their sounds).

Pretty much what leileilol said.
The 233MMX by itself has most of DOS covered.
With an AWE you cover SB16 plus the added bonus of the AWE stuff, not much difference between the 32 or 64 so I'd go for the extra bragging rights of the 64 Gold

Would be wrong not to use a GUS if you have one and any games that really shine on GUS are well suited to a 486
If you wanted you could add the SB16 here as well to cover the GUS's shortcomings and gain true OPL.

Assuming the K6 spends most it's time in Windows, so the Audigy is best choice here. If you do drop back into Dos I'd add an ISA card and the remaining AWE32 isnt a bad choice at all, but in this system I'm just after the legacy support so whichever card you have left is fine

Impossible without knowing the exact AWE32 model number, but here are my recommendations anyhow. They may come across as unconventional so bear with me and read the explanations please.

486-DX4-100: SB AWE64 Gold
This is your slowest PC and the one most likely to play DOS games for pre-486 systems. A good lot of these games are best experienced on an MT-32 (or some form of MUNT emulation, be it MT32-Pi or whatever) and for this you need a bug free MPU-401. Of all the cards here, this is the only one which can actually do passable FM synthesis alongside a bug free MPU-401. AWE MIDI Synth is an added bonus for games that support it. Alternative you you could use SB16 CT2230 and GUS Max in this system together to get perfect OPL3, perfect SB16 digital sound, GUS MIDI Synth and GUS MPU-401. This will require a good deal of IRQ management, audio routing and mixer settings, though.

Pentium 233MMX: SB AWE32
By this point we are probably in Win9x territory, and a card with MIDI Synthesis is a good idea. If your particular AWE32 also has wavetable header and genuine OPL3 you are doubly in luck. If it lacks either/both you can use the CT2230 here with a wavetable daughterboard instead.

AMD K6-2-570: Audigy 2 Gold
We are now definitely in Win9x gaming and you want support for things like environmental audio, and you probably have enough RAM to play around with Soundfonts. Just grab the Audigy 2 Gold for this.

I've currently got the gus max and awe32 running properly on the 233mmx. It was supposed to be the do everything machine..

Doing two new builds, the 486 and the K6 is just throwing me off a bit.

The K6 will be the voodoo 2 SLI machine

The 486 I was leaning on using the awe64 gold. Its my first time owning the awe64 gold and I wasn't sure if it was better for win9x or DOS.

Right now I'm leaning towards attaching the x2gs to the awe64 gold + gus max on the 486

Awe32 on the 233mmx

Sb16+audigy2 on the K6

Hopefully that covers all the bases

Depends far more on the OS than the CPU. I'd do GUS Max and AWE64Gold on late DOS box (P233MMX is obvious choice, I have those two on K6/2-350), Audigy 2 on Win98 system and given the small delta don't see why a third system is needed in this range. Perhaps to run different OS, but again, it's more down to OS than hardware.