re kyma:
more cards in the kyma means more complex algorithms (more sampler voices, vocoder bands, resynthesis partials, allpass filters, grains etc) *in realtime*. you can however \"render\" any process offline if you don't have enough realtime power. in this case i would presume that more cards mean faster processing, but rendering an effect before listening to it....hm. no, not for me. get more cards

if you want to know for sure, write an email to symbolic sound, they are really friendly and fast in answering.
we've got a basic system plus two dsp cards ( a total of 8 DSPs). This can run most of the preset library but is not quite enough if you want to run multiple complex effects at the same time, or do stereo morphing on two live stereo inputs in a good resolution. So two cards is the minimum, i strongly suggest you get more.
you can use the KYMA as an effects box by simply using the presets and replacing their input with your files or the audio inputs of the KYMA, but it truly begins to shine if you don't just use it like an \"effects box\"; you'll really want to learn some scripting, it's worth it (and necessary to really get the most out of the kyma). For instance if you wanted to modulate a parameter with the modwheel with adjustable depth and add the value of a GUI fader called \"offset\" as an offset between 0 and 1000 hz you'll have to enter something like this into the parameter's field:
((!modulation*!depth)+(!offset*1000)) hz
the \"!\" declares the following string (or \"word\") as realtime variable and creates a GUI element with the same name (except if the variable is one of the predefined ones like midi-modwheel or notepitch etc). the \"hz\" declares the unit used. depending on the context this could also be \"nn\" (note number), \"ms\", \"samples\", \"days\" (!!!) etc.
to be able to switch this modulation off with a GUI switch (leaving just the \"offset value), multiply it with a toggling switch
((!switch*!modulation*!depth)+(!offset*1000)) hz
(when the switch is set to \"off\", its output will be zero which results in the first term becoming zero, too....when the switch is on its output is one which is neutral and leaves everything untouched).
so.....is this a steep learning curve? sort of. but it's not rocket science.
mastering....the only advice i can give you in this regard is to let someone do it that knows what he's doing. it's an entirely different beast than mixing / sound design.