I suggest you contact Axiom directly. I am confused about your removal question-- the only removable part is the 1/4 to RCA adapter, which you've said you switched out ( and therefore you were able to remove it!)
If that 1/4 to RCA plug is out, you can directly plug an xlr cable into that port--the 1/4" jack hole in the middle won't stop you. However, I suspect that using the XLR to RCA you cite will not help much. Again, contact Axiom.
I am the Doctor, and THIS... is my SPOON!