XLR waste of time ?

The main issue is that your Moon LP3 does not accept a balanced signal, and does not output a balanced signal to your pre-amp. If your phono stage was fully-balanced, and your tonearm cable was fully-balanced, then it would be advantageous to used balanced interconnects.

I second Nrenter and the others here.

yes, it is waste.

Yep, I agree with everyone else. Except what Ghostrider says is not totally correct. In fact the Ayre IS a fully balance piece, and in order to take advantage of that you do need to access its XLR inputs and ideally drive it with a balanced signal. If it is wired like my P5Xe phono stage, then the RCA inputs will drive the Ayre in single-ended mode; the RCAs are not wired "like the XLR" inputs. (My p5Xe has switches on the rear panel labeled "BAL" and "UNBAL". You throw the switch based on the input and use the relevant input jacks.) But read the manual on the K5Xe to be sure I am correct. I can only speak about the P5Xe. Its possible that the K5Xe will sound best driven via its XLRs, even though your source component does not output a balanced signal. Charles Hansen probably has an opinion on this.

You may also want to consider whether you can find XLR connectors that are as good as the best RCAs.