You have not as yet "heard" your LS26, as suggested above it needs time to break in. I have about 350hrs on my LS26 and I still hear changes (for the good).
I don`t normaly like "adaptors" because that introduces another connection plus one that is not soldered.
I also use a new ARC PH7 phono which has only RCA out.
Just to see what happens if I took the "balanced" path, I ordered 2pr. of Cardas RCA to XLR adaptors,($75 a pair) balanced going into and balanced comming out of the LS26.
The difference was VERY significant, like a veil lifted, dynamics and high transparency, sense of space and depth was MUCH better, I am not going back to the RCA only path.
Some reading this will say I am imagining the improvements, but I think the signal just going through the balanced mode is improved and past on down the line so to speak. The LS26 is the only unit in my system that can go Balanced, you may find that the adaptors are all you will need.