Cats,
> I have Mackie 1402 and want to buy new soundcard with 8 ins/outs ... but whats the benefit of having 8 outputs? <
No advantage really. Since you said "sound card" I assume you're using software to record, so that's where you'll do your mixing and EQ etc. Multiple outputs are useful only if you want to patch individual tracks to play back through outboard gear. But that loses much of the advantage of recording in software: saving the exact state of a mix with all effects and knob settings, and full automation.
When I set up project studios I send each mixer's direct out to one channel of the sound card's input. But I connect only the first stereo output pair from the sound card for monitoring and playback. If everything coming out of the computer is on one stereo pair, then you know you are hearing the exact mix being created in the program. And then you can bounce to a single Wave file to create the final mix, confident it's the exact same mix you just heard.
--Ethan