Spectrum Analyzers.....

I tried to do that recently, didn't really seem to work very well. I got a really weird, thin sounding mix.
It is not as easy as just capturing the source spectrum and applying it to your mix. Some adjustments are to be made, but it helps to show you the direction if you are as unexperienced as I am. There are these up and down buttons that adjust the amount of frequency adjustment and I reduced them, because CurveEQs suggestion sounded pretty weird to my ears, too.
 
I'd rather use both my ears and eyes.

Noone wants you to disconnect your speakers and use only the analyzer ;)

It is only a valuable tool which you can use to your advantage.

More tools = more options.

Well.... you're right but the problem is that these things are not exactly accurate as far as I know...

hmmm... I don't know, I'm just a bit old school I guess.