[dggopal]

So I order the O2 amp with their standard gain settings (2.5x, 6.5x) and their standalone Odac.  Now after shipping I read that their Odac perfoms best if the O2 amp has the medium gain settings( 1.0x, 3.3x).
 
Considering I may want to upgrade my gear down the road, I want to know if I should send the amp back to get the medium gain settings or if the standard gain settings will be more open to upgrades later on down the road.

 

[GREQ]

With the settings you ordered, you'll probably just leave it on 2.5x because 6.5x will probably be unusable due to VERY high distortion. 
I've only ever had ONE vintage and VERY difficult to driver headphone which accepted the high gain setting. On everything else I can clearly hear distortion.