I'm not really sure what the question is?

Personally, I pair AGP with Win98 as plenty of faster/better/cheaper pcie cards exist for XP.
I'm not too concerned with DX versions, Take the Ti4200 for example, my Ti4600 is installed on a PC with DX7 installed. I'm more interested in the cards ability to give higher frame rates at higher resolutions then making full use of all the cards supported features.

So yes I'd demote the Ti4200 to the Athlon
The Radeon 9800 in the Dimension 8200.
The HD3650 with the ECS P4M800Pro

Or basically put the slowest GPU with the slowest CPU and work your way up.

None of these systems make for a fast XP rig so definitely agree Vista doesn't make any sense on any of these builds unless simply to mess around with.
Main benefit of the Live! over AC97 is EAX which still works natively in XP. Vista would break this

My previous XP rig (the first time around) was a MD8386 Medion, which was PCI-E, but only has an X740XL, so the 9800 Pro would probably be a slight downgrade on that, but the HD3650 would be a definite upgrade - and it had a 3.2GHz P4 640 (HT), while my build has a 3.4GHz Pentium D, so that's a little better too - only weakness is the single channel RAM that doesn't reach the full FSB.

Just collecting my thoughts, and think I've pretty much ruled out the Unichrome, and yes, very much a mess around build, thinking... too good for 98, I tend to see 98 belonging with Socket 7.

I do have other potential XP builds, though one is worse... A64 Athlon (PCI-E) and not sure if the board would take an X2 - and they are also a hell of a price in S939 (did see one a bit more reasonable).

Come to think of it, I have a compact little Optplex 745 with a Q6600 and a R5 240 low profile (hmm, no XP driver, though there is for the very similar R7 240... looks like 14.4 does support it)
And a FX4100 that isn't doing anything other than testing a forced W11 - with a GT640 (oh, and it DOES have XP drivers) - low end modern card, but would run rings around the HD3650. And a spare GTX 460 - yes, that sounds promising, I may well make that my ultimate XP Retro

No, I really want to play around with cards that were a hell of a price the first time around, wonder if I can find some old price lists. Got more nostalgia for AGP, even though the best card I had at the time was a Geforce MX440

I have a very similar "project" going on these days. Still in the process of finding out where this is going to.
Initially I was thinking about a Win98/XP dual boot AGP-system made from parts flying around that would otherwise live stashed away in their boxes forever.
But for now it's a messing around machine with Win98 only. Still undecided if to add XP or not. I know for XP there are better options and Win98/XP dual boot will never be the best of both worlds.
Since I already have a (lower end, socket 7) DOS/Win98 machine and also a Win7 system (which will run most XP stuff I guess) I'm not sure if this would gain me anything.

The board used is a Asus P5VDC-MX, combined with 1.5GB DDR-2. Sadly no C2D support here either...
CPU is a Celeron 360 3.46GHz @4GHz. I chose that in favour of a Pentium D 9xx/8xx because of the lower TDP and because Win98 can't use a second core at all. If it's the better choice performance wise idk/haven't tested yet.

Video cards I've tested with this machine up to now are: Ti4200, FX5200, Radeon 9600Pro.
The Radeon performed best in terms of 3DMark99 to 2001, followed by the Ti4200.
The FX5200 was 10-20% behind the Ti4200 while the 9600Pro was roughly the same amount ahead. The few games I've started up showed the same picture with the Fx5200 drastically falling behind the Ti4200 (which may be a well known phenomenom to the experts here!?).
I'm planning to also test a Radeon X700 (one with the slowish 250MHz DDR-memory) but this is work in progress. First results show it only slightly ahead of the 9600Pro which may be a CPU limitation. Not sure if that can be possible. So for now the 9600Pro looks like beeing the better overall choice.
I also can't recommend using the on-chip Unichrome since that made my Win98 installation unusable right after driver installation.

ChrisK wrote on 2025-01-08, 13:45:

The board used is a Asus P5VDC-MX, combined with 1.5GB DDR-2. Sadly no C2D support here either...

https://www.cpu-upgrade.com/mb-ASUS/P5VDC-MX.html - unless it's a 2.00G board revision, when it will support C2D 6000 series

If you gona use only Windows XP + some newer OS if you want then i would go with HD3650 and Catalyst 7.11 for older games and XP.

Matth79 wrote on 2025-01-08, 16:52:

ChrisK wrote on 2025-01-08, 13:45:

The board used is a Asus P5VDC-MX, combined with 1.5GB DDR-2. Sadly no C2D support here either...

https://www.cpu-upgrade.com/mb-ASUS/P5VDC-MX.html - unless it's a 2.00G board revision, when it will support C2D 6000 series

Yes I found that too.
The critical point is the used voltage regulator standard.
C2D uses Intel VRD 11.x, older P4 CPUs VRD 10.x.
Both standards differ substantially in the VID codes, so no trivial hacking possible.
P5VDC-MX v2.00G must have VRD11. Mine is v1.03G...