Passive preamp to a power amp?

I was reading reviews on the Schiit Saga and people were having a hard time differentiating between active and passive mode. In that case, why not just get the Schiit Sys passive and save 300 dollars? 

I'm sure I'm missing something fundamental here.

p.s. Sorry for the deluge of newbie questions. I hope others have the same questions at some point and benefit.