Recorded mixes too quiet

Hi there. I'm relatively new to rekordbox and far from an audio expert so I'm hoping ya'll can help me out!

When I'm recording mixes I of course keep an eye on my channel levels and try keep them nice and full without going into the red. Same goes for the MasterOut meters that show the recording volume-- always sure to keep them as full as possible without clipping. 

But when i finish my mix and save the recording, when I playback the recorded file in iTunes, the volume of my mix is significantly quieter than most of my iTunes files. 

Same goes for when I upload the recorded file to my SoundCloud... compared to the average mix or track in my stream, my mix is way way quieter. 

I've played around with headroom options in Preferences > Mixer > Output but if use a setting higher than -12db my MasterOut levels get pushed into the red even if my channel levels aren't... and I assume this clips my output sound. 

So, are there any specific settings I should be using to get a more "standard" volume for my recorded mixes? Would be great to know what settings to double check and where to find them. If not, is there a 3rd party tool/application that you guys recommend to boost the volume of my recorded file that won't clip the sound? 

I'm using a DDJ-RB controller if that matters. 

Thanks for any help you guys can lend!