XLR versus RCA connexion for NAD M12-M22 combo

[mjb]

I am willing to spend US$ 100-200 to replace them and would appreciate some opinion on whether, in this price range, XLR cables would have a chance to sound better than RCA cables.

Fwiw, my opinion, definitely! I would always use XLR's when available, no question. A cheapie balanced XLR cable from a musicians store would be preferable to "crappy RCA cables".