Thank you a lot for the kind words and some very detailed feedback, timaeus222 and Slimy – this is exactly what I need especially EQ and mixing, since I'm kinda new to those. I'll make sure to make a new post here once I've found the time to sort these problems out
By the way, you're right when it comes to the timing issues, timaeus222. 99% of this is recorded MIDI, and I decided to check what the response would be if I did no quantization at all. I'll correct the worst cases, since the timing errors stuck out.
Perhaps I should fire up Famitracker and make some white noise brush drums, so we get the real thing? I kid, I kid Again, thank you!