For DJ’ing purposes, reliability, portability and simplicity are key. If you have a laptop with a PCMIA slot then the Echo Indigo DJ card is absolutely fantastic. It is by far the smallest solution; it sounds great, works reliably and is perfectly suited to DJ’ing.
I have a much more comprehensive audio interface with multiple outs. This is useful when I route audio to separate channels of an external mixer – my DJM600 for example. However, in nearly all cases I prefer to use the Echo Indigo for DJ’ing and route all channels via the Master Out within Live.
Setting it up for headphone cueing is easy once you have the hang of the control panel. It’s even easier when you have Vinkalmann’s Guide to using the Echo Indigo DJ Card.
I also set the control panel so audio from other programs like i-Tunes or media Monkey go to both outs at all times. This way I can listen on headphones or via my Monitors without having to switch any cables or plug headphones into another slot.