Reply to Headroom

I've already read some info about headroom and Traktor, and experimented myself.

(-3 to -6db seems to work fine for me).

When connecting a S4 into an external mixer, this gives me plenty of room on the S4's various knobs to adjust volume or EQ levels while still keeping it sounding good.
Am also keeping way off the red easily.

Anything else one needs to know in this regard?

PS : The external mixing I was working with had master and cue level led's - is this standard with most mixers?