Xonar Essence STX and Speakers

A few questions and peculiarities about my sound setup consisting of a Xonar Essence STX card with SP2500 speakers:

First, I was unable to get any sound whatsoever until I switched the analog out in the ASUS control panel FROM 2 speakers TO headphones whilst having the speakers connect to the card via the headphones jack; however, the manual states that this should not be done. Is it really that big of a problem and am I losing quality by doing this? If it is a problem, how can I go about fixing it?

Thanks!