Hi. Just registered after years of lurking..and lately, running into issues with a 90s IBM desktop.

The machine in question is equipped with the original hardware from '98 other than a ram upgrade (from 64mb to 256mb), hdd caddy and a slow Windows 3 era ISA ethernet card: amd-k6-2 3D 300mhz, acer v70ma motherboard, dog slow onboard 2mb mach64 graphics, tiny 100w psu (using a full size 250w one to test though). The machine was hardly used since new, with the original 6gb Bigfoot HD still functioning and almost nothing installed onto the factory OS. Still need to image that drive...

I have tried the following PCI video cards: ATi 9250 256mb, ATi (Diablotek) 7500 64mb, nVidia FX5500 256mb and a ATi Rage XL 8mb. With the 9250 and 7500 cards, the CPU fan spins but the machine never POSTs or beeps. With the nVidia, it will go into the BIOS just fine, showing "NVIDIA" as the video controller and 262144kb as the video memory - however when actually trying to boot it just hangs at a blinking cursor, making no attempt to read off the floppy, cdrom or hdd - and ctrl+alt+del does nothing at this point.
The RageXL works just fine. The performance boost is negligible however and the picture quality is noticeably worse than the onboard graphics. At least it ruled out the PCI slot being bust?

What I've tried:
As mentioned earlier, using a much higher wattage PSU than the one it came with.
Removing the ISA ethernet card.
Updating the BIOS using IBM's official tool.
Changing around VGA interrupt jumper.
Mucking with BIOS PnP and IRQ settings.

This page has more info about the mobo:
https://theretroweb.com/motherboards/s/acer-v70ma

Any ideas of what else I could try, or are these cards simply too new and I should go hunting for something like Rage128 maybe? I just want stuff like Rollercoaster Tycoon 2 to not devolve into a slideshow on it, and possibly Asheron's Call to work without spitting out a DirectX error.