Specular Color, Alpha and DXT

puh, pretty complex, that formats, materials etc.
What is Specular Color/Power (FSDS) used for?
Which is the best quality format to save a texture in if I want to include an alpha channel?
best,
rev
What is Specular Color/Power (FSDS) used for?
Which is the best quality format to save a texture in if I want to include an alpha channel?
best,
rev