I FINALLY found where it goes wrong, and why it always has been an issue.
I cranked up my speakers so I could hear both speakers well. I had them on one at a time, to listen. They sounded different. I found it strange, and actually feared it was the speakers themselves.
But I was happy to find out its the cheapest link in my setup: the interface.
I A/B tested the sound of each speaker through each output. I unplugged one cable from the output of my interface, and listened to the same speaker on each output. One was always different. Same result with the other speaker.
Simply put: the Output 1 of my 2i2 has an issue with the sound, while Output 2 is way better. Output 2 has that crunchy treble and the tight bass. Output 1? Flubby bass, muddled mids and treble that just disappears in the mess of the rest.
With both speakers on, I've never been able to compensate for it settings wise because of the vast difference. It's always too much on one, or too little on the other.
So I'll be looking at a new interface now I guess