the problem is that drivers that depend on other drivers will fail with SAD.
This is not an issue when slipstreaming the DriverPacks into the source.
With the MS tool DPINST.exe there are limits that do not exist with windows setup.
I don't recomend attempting to install a clean system with SAD. it is good far adding a device or for updating existing drivers.
If you insist on a software first install then it will take several passes with reboots in between. For example a HD Audio driver depends on teh HDA bus to be installed first. if the HDA bus is not installed then the HD sound driver will not install. (because teh device does not exist). Same goes for like a SCSI tape backup. You must first install the SCSI adapter driver reboot then install the Tape driver.
Using SAD on a machine with no drivers may take three passes and two reboots.
the reason is simple all devices are conected to the chipset driver... the chipset driver must be installed first (pass one with SAD), then the machine msut be rebooted then the devices that are connected to the chipset can be installed (pass two with SAD). This is not a bug or a shortcoming with SAD. It is simply the way PnP works... think of it like building a pyramid, you can't put the capstone on first, you must start at the base and work your way up to the top one level at a time.
If you don't like this then use the DISC method to slipstream the DriverPacks into your source... That is what it's for