I would....

486-dx4100 with both VLB and PCI
Tseng ET4000 VLB - VLB is 1/2 the fun of a 486
Gus Max, maybe paired with a Creative card.
This would be your dos rig, Cant think of any games that shine with a GUS don't need anything more then a 486

Pentium MMX 233
NEC PowerVR
Voodoo 2 SLI
SB AWE (32 )
Bit of a test box to play around bot dos and Win9x games, PowerVR, SLI. Truth is though between the 486 and later builds this doesn't give you many benefits

Supersocket 7 K6-3 450
Voodoo 3
AWE64
This is your glide focused build, ideally I'd want a better PCI card like Creative SBLive-Audigy 2 or Vortex card though for windows side of things

Pentium 3 866
GF4 ti4600
Audigy 2 ZS Gold
This is your Win9x D3D focused build

Might be needing the Mach 64 in the 233MMX if that PowerVR is an addon card.

Personally I like over-speccing systems so I know CPU and RAM won't be bottleneck.

I have a GF4Ti, V2 SLI and Audigy2, but pair them with a P3-1400S and still consider it a bit slow for some of the last Win9x stuff. I also upgraded my late DOS box from Pentium 200MMX to K6-2 350 to P3-600 for the same reason.

So... I'd go with a really beefy late DOS box:

P3-866, Voodoo3 (purely for 3dfx's excellent DOS VESA support), GUS Max and AWE64, running DOS 7.1

That leaves some slower CPUs and VGA/GPU and sound both older and newer.

I'd aim for a 486DX33 for stuff too speed-sensitive for the P3, even after downclocking and disabling cache, the 486DX4-100 comes closest, but still too fast, basically. That could be paired with the ET4000 and whichever of those SB16/AWE32 has real OPL3.

- 486-dx4100 with both VLB and PCI
Tseng ET4000 VLB
Gus Max

- Pentium MMX 233
PCI ATI Mach64
Voodoo 2 SLI
Awe32

- Supersocket 7 K6-3 450
Voodoo 3
NEC PowerVR (overclock your PCI bus!)
CT4500 Awe64

- Pentium 3 866
GF4 ti4600
Audigy 2 ZS Gold