Normally, when speaker flags are used or multi-channel stuff is played, BASS will give DirectSound a speaker arrangement to use via the "dwChannelMask", as described here... http://msdn.microsoft.com/en-us/windows/hardware/gg463006.aspx
But when the BASS_DEVICE_NOSPEAKER flag is enabled, BASS will use dwChannelMask=0. So I guess it is that that is causing trouble for the Saffire card. In that case, I think you will probably just have to leave out the BASS_DEVICE_NOSPEAKER flag and put up with the swapped output order.
What Windows version is being used? How many speakers is BASS detecting (see BASS_GetInfo), and is that correct? If it isn't correct, you could try using the BASS_DEVICE_CPSPEAKERS flag to have BASS get the speaker count from Window's control panel (pre-Vista).