I don't know if there's really any differences between the XPS2 and the M170 BIOSes.
As far as the differences between the A01/04/05 versions, you have to flash to the hacked A01 BIOS as it's, well, hacked, to allow you to flash it to a 9300. Otherwise, it detects it's a 9300 and won't allow the flash. Once you've flashed the hacked (A01 BIOS), you can simply go to Dell.com and download the self-executing M170/XPS2 BIOS flashing programs, and update to the latest & greatest version. You don't need to use the bootdisk program or type anything in.
The difference I know of between A04/A05 BIOSes is that the BIOS settings for the cooling fans changed, and the A05 BIOS turns the fans on later, supposedly saving battery life.