Here's another thought on this balance issue, what tracks sound best on a rig, there's usually a track that someone drops (or an entire set when you've got a bright spark for a dj) that sounds an order of magnitude better than everything before it.

My clubbing is mostly done in a confused haze but somehow I know that a Nukleuz track called Instrumental sounds bloody amazing at the Fridge down in Brixton, as does Mauro Picotto's Awesome (my copy of which seems to have gone mysteriously missing, those bastard record pixies messing my records up again!) and First Strike by Signum.

The top end sounds sweet on all these and the bottom end works in wonderful ways ... so when I'm working on styles that could be DJ'd with these tunes I balance so they mix well together.

Any other suggestions ?