yeah this is probably true, something i came to the conclusion about this year.kilroy wrote: That's easy, mate.
A great EQ.
And a great compressor.
Unless your mix is totally fubared, these two tools should handle better than 90% of any mastering job worth attempting in the first place.
but im going to give a cliche'd response to the original question and answer that the most 2 important tools are your ears and your heart.
we are lucky to get to experiment with different effects i know for a while in history people had to purchase hardware effects and they learned how to use them really well. but if you play with an effect and you hear a significant improvement in the sound on a variety of soundsystems, then you are free to add more to your chain than just an EQ and Compressor.
I have found that the instrument sounds I use in Sonic Synth 2 and Sampletank are really high quality and have great DSP with them so my tracks need less effects on the master chain - always start with great sounds and then your mastering process is easier!
It seems to be so three-dimensional, open sounding, it fills the room and is brillant (made without an exiter?). And I really liked the vocals (Vocoder or even Melodyne on that?) 
