Nice, seeing High Sierra running on this old but capable system! It rocks with a new ASUS GT1030
6 GB DDR2 RAM
Asus GT1030 2GB
Sandisk SSD 128GB
TP-Link AC1200 Wifi USB
Inateck KT4006 USB 3.0 PCIe (No boot)
A good deal of DSDT editing was necessary to get this machine to boot High Sierra but finally it works flawlessly, even sleep and wake!
You NEED to have the DSDT put in place for installation because otherwise macOS doesn't recognize the SATA ports.
There are a few important BIOS settings: SATA hast to be set to AHCI and "native" and HPET has to be run "64-bit", I'd recommend to disable IDE and the serial and parallel port.
For the GT1030 nVidia Webdrivers are needed, have to boot with nv_disable=1 until you have them installed.
You have to install Clover in legacy mode because this old fella does not support UEFI.
Only downside: The so often recommended Inateck USB-card isn't recognized by BIOS, so you cannot boot from it. It works perfectly within macOS though, have the ac-Wifi connected to it.