Really, it's the graphics card that limits you. 9x and below you want something like a GeForce FX or below for best compatibility, but this limits you for later games.
So it doesn't make sense to install a GF FX on a LGA 775 build, it's not going to hurt but you're not going to see much benefit.

If it was me I'd go with socket 370 and the P3 1Ghz
I find a P3 600 is fast enough for any games that don't play well on XP however faster CPU's don't cause any problems and allow you to play a few extra of those 9x/XP crossover games.

or you can go as fast as possible,
I'm not familiar with the chipsets or how well they work in 98 but both the Asrock LGA775 motherboards have AGP and 9x drivers, the Asus P5V800-MX has AGP but the web page doesn't have any 9x drivers.
Most Win9x games wont care about CPU speed, even the P3 will be too fast for speed sensitive dos games and you could swap the video card from say the Geforce FX to something faster during XP gaming sessions and keep within your 1 PC limit.

You have an interesting assortment of motherboards. Haven't googled all of them, but it looks like a LOT of VIA or SiS chipsets, and your socket 370 board has no AGP. Argh.

What is people's general view on nForce2 for 98SE? I think the general view around here is that for Socket 462 and 98SE VIA chipsets are preferred, but I'm not sure what the details are. I'd be inclined to think the 462 system, assuming the motherboard hasn't failed due to bad caps and assuming no big NF2 dealbreakers, would be the best 98SE bet on your list at least if you're not open to acquiring new motherboards.

That 1GHz socket 370 PIII deserves a great home, but given it's a 133FSB (so no-non-overclocked 440BX board), as are all of your P3s, what might that be? an i815 board? that's missing ISA so it won't have the absolute greatest DOS-friendliness, but otherwise that might make a nice 98SE system. Or if you don't have a great home for it, sell it - those are likely worth a lot more than a random hotburst 478/LGA775...

The other thing is, you might be able to do an unorthodox 98SE system with those newer VIA-chipset hotbursts - are any of your hotburst motherboards AGP?

That S370 board does support 133FSB but I missed the lack of AGP. Pair it with say a PCI voodoo card for great 9x system but that's not in keeping with the "trashware corner" theme so have to agree is out of the running.

Personally I like nvidia based motherboards. Maybe not as stable but are a bit different and interesting if you enjoy messing around with old hardware.
However I tend to think once your over the 1Ghz mark it's already crazy fast for 9x so no harm in going faster.

S. 370 mobo with PIII 1000. Sell the rest of the "trash" and buy a Voodoo2 (or two for SLI). This PCChips mobo has descent SB-compatible near 100% correct OPL3 FM synthesizer clone build-in sound chip (rebranded CMI8738) and its integrated video will work fine with Voodoo2 for 2D VGA modes.

Back with a few updates, I has finally the time to get back to the Build.

Available soundcards are two Sound Blaster Live 5.1, a SB0100 and a SB0220

Video cards are all AGP:
ATI Rage 128Pro Ultra 32M SDR
nVidia GeForce4 MX440-8X 128MB DDR+TV
GX-G2M4LP/64M/TV
Radeon9600SE 128M DDR V/D/VO
Radeon9600 Pro Advantage 256MB

The Socket 462 decided to let two capacitors blow as soon as I powered It on.

I also have a 775 MoBo with everything compatibile with Windows 2000/XP (and should be also with w98), so the "old" Build purpose have shifted to DOS(mostly) and W98(less important).

Now the question are: would it be worth it to replace the capacitors on the Socket 462 board to hook up one of those cards to the AGP for better performance and compatibility (mostly under DOS, 98 as a bonus) or should I just stick with the Socket 370 MoBo and its integrated GPU (that MoBo has no AGP slot)?
Which SB card would be better?
Given the above is the Socket 939 board a decent fallback option instead of recapping or is it almost the same as a P4 board regarding DOS and 98?

Edit:
I also tried looking for the prices of a Voodoo 3 2000 PCI card, but those are around 200+€, which Is absolutely out of budget, would a TNT2tm64 PCI graphic card give comparable results? The prices for those look far more approachable

Thank you in advance guys

Personally, when a family member intrudes on my old-HW, it only does great damage, some of my most interesting pieces are vanished, given away or thrown away.
If you wanted to buy them back today, it would be quite expensive, and the search could be complicated.
I couldn't get rid of anything, but the idea of ​​having a PC in place of some, which can simulate the slower ones (obviously), can be correct, if instead you want a not so old PC (775), which simulates all old PCs, well sorry but you lose the charm of the old machine, for example a P4 423 with RIMM, even if a 775 could equal or even improve the performance, for me it's something else, then the idea of ​​selling part of the hw to buy more, it could be done but, for expensive cards it takes a lot, perhaps by finding someone willing to exchange, you could keep your favorite PCs, and get what you need.

RobbieBenzi wrote on 2024-01-23, 21:13:

... Video cards are all AGP: ATI Rage 128Pro Ultra 32M SDR nVidia GeForce4 MX440-8X 128MB DDR+TV GX-G2M4LP/64M/TV Radeon9600SE 1 […]
Show full quote

...
Video cards are all AGP:
ATI Rage 128Pro Ultra 32M SDR
nVidia GeForce4 MX440-8X 128MB DDR+TV
GX-G2M4LP/64M/TV
Radeon9600SE 128M DDR V/D/VO
...
I also tried looking for the prices of a Voodoo 3 2000 PCI card, but those are around 200+€, which Is absolutely out of budget, would a TNT2tm64 PCI graphic card give comparable results? The prices for those look far more approachable
...

An ATI Rage 128 Pro Ultra, A TNT2M64, and a Voodoo 3 2000 are all around the same performance, with the Voodoo 3 being a lot worse at resolutions > 800x600. Can run Quake 2, Half-Life, but not Quake 3 well.

The Geforce 4 MX 440 is 2-4 times faster than all of those cards, has not very much resale value (worth keeping), and it can also run Quake 3 smoothly.

The Radeon 9600SE is similar in speed to the Geforce 4 MX 440 but can run higher resolution, and more modern games that support DX9.

To run Doom 3 you need something about 4-5x faster again, such as a Geforce 6800, 256MB GDDR3, AGP 8x. The shadows in Doom 3 are a CPU bottleneck.

Depends on where you want to draw the line...