Thank you very much, Dietz! Your words mean very much to me!
And thanks for your suggestions! Okay, the low frequencies - guess I'd know what to do (Guess it's my little home studio room that has some bad low frequency response and low freqs are getting annoying very quickly so I tend to mix with little lows - have to use my new headphones a bit more, I guess ;) ) but do you have any tips how to get the instruments more separated? (Use of EQ to give them their "isolated" frequency range? Or something that can be done in MIR Pro spatial wise?)
The original WAV file is a bit better, though. Soundcloud's MP3 compression is well known one of the worst out there ;)
Marco