I have some old equipment and fancied make a retro capable machine (for Windows, DOS, AROS and maybe even OSX). I'm mostly concerned about the setup with Windows 98 being the problem child.

My mobo is a Gigabyte G41M-ES2L rev 1.1 https://www.gigabyte.com/uk/Motherboard/GA-G4 … -ES2L-rev-11#ov which has this layout:  PCIe x1 / x16 / PCI / PCI
It has onboard Realtek ALC888 and RTL8111 gigabit LAN. Mobo of course has no UEFI but also has no AHCI options (just SATA modes and Legacy IDE emulation modes)
CPU is a E5700 Pentium DualCore at 3-3.6GHz and Ram is 4GB of DDR2-800. I don't want to put less Ram on as XP will be happier with more.

I have these suitable cards:  
PCIe VGA Radeon HD 4670 (will block one of the PCI slots)
PCI VGA Nvidia FX5200
PCIe Sound CMI8738 (these use PCI bridges) 
PCI Soundblaster 128 PCI
PCI Soundblaster Live!
PCI Network RTL 8111 (gigabit) and RTL 8029 (from memory) (100mbit)

Initial thought is to use the Radeon HD4670, Nvidia FX5200 and onboard bits only if I dont need to use the cards but I wonder about DOS?

Windows 98 (and hence DOS?)

I do have Intel chipset drivers (community?) for the mobo. There are also drivers for the onboard sound (AC97 only - how do I make the onboard only work in AC97?) and the onboard LAN chipset. But the Radeon HD4670 definitely won't have drivers. So, I have to use a PCI FX5200 - how to make Win98 use that card but Windows 2000 and newer use the Radeon?
What happens when rebooting to DOS mode from Win98 - will the sound and LAN still work?
Also ACPI - use the switch to disable when installing Win98? Or not? Best to keep it on in BIOS for later Windows I assume? Plus I will need some memory patches?

Windows 2000

I have drivers for everything. The HD4670 driver is a community driver that works despite the Radeon being a 2008 card launch!

Windows XP

Pretty much everything works fine with XP

AROS

This is an Amiga-like OS. The Nvidia has native support but the Radeon only VESA support. Not sure it matters much. All 3 sound cards and even onboard sound and LAN will work. Does not support GPT reliably

OSX

The Radeon HD4670 supports OSX from version 10.6 to current so is a good card for this purpose. From memory, I'll need kext mods for the lack of AHCI or similar. CMI8738 and SB Live will work with drivers.

Installation Order (Windows only)

The media is either a 250GB SATA HDD or 240GB SATA SSD (in IDE legacy mode)I assume 98 (then I believe there is some sort of partition fix I will need) before 2000 and XP. 
I'm gonna need some of the Rloews (great guy, RIP) patches - are they really now free?

Anyone any helpful advice, gotchas or constructive criticism of my ideas?