NetImmerse & bits created by DES
You can expect PE to run at full 32 bit. The memory bandwidth and high fillrate capabilities of modern graphics cards offers good enogh performance to motivate 32 bit graphics. Not to forget, it looks better, and also 32bit z-buffer offers far better precision. The hardware requirements will (probably) be based on adequate performance in 32 bit. Voodoo 3 or below will not be your best choice, but that is true for most games anyway.