Downloaded the software and, the fact is that, it DOES NOT recognize the sigma raw files!!
Downloaded the software setup file but it didn't like my computer (Windows XP Pro SP3).
Anyhow, many will agree that SPP provides the best conversion
of X3Fs, but less than adequate post-processing. For this reason, a popular serious workflow is to convert into as neutral a TIFF image as possible and to move onward to one's favorite editor to complete the job.
That's my basic recommendation, especially to owners of cameras more recent than my SD10
It's your choice for SPP working color-space and bit-depth of output - every has their own preferences and that subject has been beaten to death elsewhere.