Currently media-sound/xfi-drivers require CONFIG_SND_DRIVERS and CONFIG_SND_PCI, but these 2 opotions appears only from 2.6.27. I managed compile media-sound/xfi-drivers with 2.6.25-r6 with modified ebuild. Diff attached :).
Created attachment 171555 [details, diff] diff for xfi-drivers-1.00.ebuild to support <2.6.27 kernels
Forgot one thing. Driver works perfectly! Thank you!
Fixed. Thank you for reporting.