I also think having the mix in mono and then just having one sound as a lick in stereo. It sounds like it realy stands out in the mix and grabs your attention. I think this is coz your ears are so used to hearing the mix in mono and knowing exactly where the sounds coming from (dead centre) then suddenly you get the stereo sound and it sounds more emphasized as your ears are focused to the middle. Bit like in a4 - glenn wilson - enemies (alexander kowalski remix) when the synth comes in. I was told about a way of exapanding the stereo spead using something called the hass effect, this is basically a slight delay (25ms ish) on a sound and panning the delayed one to the left and the unaffected signal to the right. The brain will always hear the first (undelayed sound) and the second will be masked out even if you keep the levels the same, so the sound realy is not panned at all yet the delayed side will sound slightly quieter. Then as you move around inbetween the speakers the delayed side can actualy be noticed depending on your position within the room. Check out the speedy J loudboxer lock grooves, they have a wide st image and i am sure hes using effects like this but pobably in a more extreame way (maybe longer delays). Seems to pan his reverbs around a lot too. Alot of effect units use this effect along with reverbs making them sound wicked when realy its the lil delay thats giving it that extra edje.