I use iZotope Ozone 5 for mastering. It has a great volume maximizer and that is only one of the 6 “effects” that you have. You get all kinds of controlling over the sound that I just don’t have time to write here about. But getting -6dB Integrated Volume without any distortion is very easy.
It’s not a cheap software but it will drastically change the sound of a song when used correctly. Send me a song and I will demonstrate: tommi@rockworksstudio.fi
wrong.
Yes
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Hehe. Ok, thanks. 
I like what Izotope did with Insight. I like loudness curve, how loudness changes over time. I noticed if curve sits arround -10dB, then level is fine. -23dB is way too low for audio. In cubase -10dB is not visible, at least it wasn’t last time I tried. Would be good of Steinberg would make it so that it is visible up to 0dB. I use steinberg 128 plugin more, seems more flexible.
A better tool for mixing, IMO of course, is the K-System. Set the Cubase meter to K-20 and don’t go over the 0dB mark. Done! The mastering engineers will love you for it since you will be giving them all the headroom they could want. Don’t sweat about EBU R-128 yet, unless you are require to deliver in such a format. The broadcasters will take care of that if they do use it anyway.