If I look at the high end of W98 GPU's, I can buy a Ati 9600XT or a Gefore 4 TI4200 locally for 50 or less. Would those be a good choice to do all the 2D stuff, all the old and new stuff, and have the Voodoo2 SLI to do the Glide stuff in between? Or any thoughts against such a choice in my system (P3 733 coppermine, 512 MB RAM, DX9).

I know that at AGP4x I will not get the full potential out of those cards, but that is not the purpose here (I have a 2010ish XP system that runs circles around it anyway). The purpose is to get full potential out of the P3 W98PC that this is.

Any preference of one over the other, or alternative choice?

Next thing you'll end up doing is upgrading the CPU... it always goes this way 😀

IMO the cards you've mentioned are good. From compatibility point of view i'd prefer nvidia, but that's just me. I also do not use 2d stuff all that much so can not say anything about that. If you do not mind newer you can also take a look at GeForce FX cards - the system will still make sense - upgrading the videocard without replacing whole system is a common thing.

Something like FX5200 may be a good dirt cheap option to try, it is low end card which is often slower than older cards, but is also fast enough for many games from time period you've mentioned, has great compatibility and should be nearly free.

I had been thinking about the cpu, but I think I'll leave it at 733; the old games run stable and the Voodoos icecold. And the mobo only goes to 866 anyway.

I can buy an MSI fx5200 for 10. Now, the price difference with 40-50 for the other cards is small in absolute terms. Would I be leaving a lot of performance on the table going with the fx5200 instead of the aforementioned high end cards? According to this video (which is not my system; if you'd run a heavy game CPU bottlenecked it's a different story of course) between 50% and 100% better:

https://www.youtube.com/watch?v=8kzlih1X6J4

So I'll think I'll splash out on the Geforce Ti. It does fit the theme of the "slightly reasonable best of the best" like the Voodoo2 SLI and 512MB RAM do in this W98 PC. Would the Ti make the Voodoo's obsolete in this system? myeah, for D3D and generally the newer games it would. But the Voodoo's are still a feast of performance and compatibility for the Glide stuff.

Yes, FX5200 is slower. But, especially if you find 128bit version, it is not bad and can run older games quite well. I mentioned it because IMO it is a good option for older games - cheap, abundant and great compatibility. Very few AGP cards are so easily available.

At least where i live GF4Ti are not very common and are somewhat pricey, especially in good/tested condition with working cooler etc. If you can get one - that's good and will work very well in this system.

Also 4200 is kind of "low end" itself, among GF4Ti series. There are also 4400 and 4600. Those are even less common and more expensive.

You can also take a look at other FX series cards, there is always something like FX5900/FX5900XT which IMO are one of the better cards for 98 in general because of combination of performance and compatibility, but probably too much for your CPU.

4400 and 4600 are very hard to find and expensive here. 4200 is far more common and reasonable. FX5200 is found everywhere.