I understand the word "philosophy" used in this context to indicate a complex notion, namely, design-used-for-intended-acoustics-complementary-of-music.
In other words, there's a sound the designer has in mind -- a flavor profile, if you will -- and this is chosen based on what the designer thinks the music needs. It is philosophical because it is the application of general ideas regarding musical aesthetics to the best engineering designs to accomplish that -- and to a price point. This, I think, is what is making Schiit so successful.