In a nutshell :

The best choice for overall Performance, Image Quality and Driver support would be the Voodoo5.

Upto 4x FSAA, higher Resolutions and 32bit, large Textures ( 2048x2048 ) capable, and the highest developed Driver support existing.

AGP should be preferred, but keep in mind it is a 3.3V 2xAGP device, that many modern Motherboards do not support.
Performance loss in PCI configuration is neglectable however, since no 3dfx Card ever supported AGP Texturing (hence the AGP Aperture does not increase the amount of Texture Memory)

The Voodoo Rush is a Voodoo1 with an additional 2D Core on the PCB (either Macronix MX86251 or AT3D/AT25 Core), thus it is a stand-alone Hard.

Voodoo1 and Voodoo2 were the only dedicated, add-on 3D Accelerators.

2 Voodoo2's with the same amount of Video RAM and (ideally, otherwise Problems can occur) the same brand can be linked together in SLI. Framebuffer doubles (allowing 1024x768 Resolution), Texture Memory does not double (needs to be mirrored on each card)

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Chosing a Voodoo2 (or Voodoo2 SLI) over a Voodoo5 would only make sense for an isolated number of very old Glide Games, that encounter compatibility issues with a Voodoo5.

Using a Voodoo1 would only make sense for isolated, extremely old Glide games that encouter compatibility issues with a Voodoo2 or higher.
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Adding a Voodoo1 or Voodoo2's to an existing Voodoo3/4/5 System is not recommended, as it exhibits an enormous amount of conflicts/ambiguities between the Drivers.
If it works in isolated situations, those cards do not increase each other's performance; the System will always treat them as individual Rendering Platforms that you could (at best) chose from to run a 3D Application.

Well, simply put, the Rush is indeed a Voodoo1 as a stand-alone Card.

The Banshee is close to a Voodoo2, but lacks the 2nd TMU. Still, a stand-alone card with a massively improved 2D Core (the Voodoo Rush' 2D Core was not very fast, thus people didn't like it alot)

Effectively, you can hook up a Voodoo1 or Voodoo2 to any 2D Card, be it a normal Video Card, or integrated Video.
There used to be Problems with some old S3 Variants as a 2D partner, but there are Patches available for these cases.

Your soundcard should not matter (?), not involved in the 3D Rendering. Driver-wise, I'm not aware of any compatibility issues with any Sound Driver.

Your AGP Port needs to support 2x AGP 3.3V.
Generally, the last AMD platform to fully support that is the VIA KT333a (except for its latest steppings, CD and/or CE I think).
For the fastest setup's, that's what people often use (KT333 or KT333a)
Just check your Motherboard Manual for 2x 3.3V AGP support to be safe.

Most Pentium4 based Platforms are 4x 1.5V AGP only, thus incompatible. There was only one (I think a SiS645, not sure) that had still support for 2x 3.3V AGP.

The Voodoo5 does not take an insane amount of power.
Depending on what you have in your System, a good quality 250W power supply should do. With a 300W one, you should be on safe side any day.

Collin Mc Rae I don't know, but the Voodoo5 will play Quake 3 without any problems at good performance 

No, you're getting things wrong here :

Adding a Voodoo1 or Voodoo2 will not have any effect on the Performance of either the 2D card (which actually can be a fully equipped 3D Card), nor the way around.

Adding a secondary 3D Adapter to an already 3D capable platform can cause some difficulties, since either the Application must allow to chose between them, or makes use of a Switcher Utility mandatory.

But technically, it does not matter if the Primary Video Card is a 1MB Cirrus Logic onboard, or an ATI X800 Ultra 256MB. The Voodoo1 or Voodoo2 will work, as long as your Games/Applications allow switching to or selecting them as the secondary Adapters they are.

Voodoo1 and Voodoo2 are 3D olny, only the Voodoo Rush, Banshee and Voodoo3/4/5 have full 2D capabilities.

Well... I think now I get it (at least better than before).

I thought the fact that it was "accelerator" card meant it would accelerate the primary graphic card, which doesn't seem to be that.

So if I finally get all of that, I would make so:

1) For an old pc which has only a basic card, like the ones on the motherboard or a very crappy one, I should put a Voodoo1 or a Voodoo2 or SLI.

2) For a pc more powerful than the first one, on which I wanna play newest games, I shall put a Voodoo5.

Were the Voodoo2 only PCI?

Thanks for the answers 

Well... all I'm good at when it comes to hardware is screwing up old hard disks so don't expect too much from a newbie like my (it's even written under my nickname!).



I mean, I need some time to "assimilate" Voodoo stuff. For now I'm just so lost in here but because of I'm convinced I wanna buy Voodoo cards I'll soon feel more confortable speaking to you ol' Voodoo masters!

8)

You hit the nail on the head there, omega_supreme! 

Hey cool !  

Never heard of that one. How is that possible? did it have its own 2d part then?

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Found it, Obsidian 2 AGP, it has indeed a daughterboard