After exporting my song, I listen on my computer, to both the MP3 and WAV and they sound great.
I upload a private link to soundcloud and I wouldn't say the audio quality gets worse, but just that the entire song sounds WAY more mono. Like there is A LOT less stereo information. Why??... I tried uploading both the MP3 (320kbps) and the WAV file. I A/B how they sound on my desktop when I preview it there, vs on soundcloud. Just again sounds way more centered and not nearly as wide. Everything else sounds about right though.