OK; thanks for the clarification. So you would not be adapting between the RCA output of a component and the XLR input of another component, or vice versa. You just want to adapt both ends of an XLR cable so that the cable can mate with the RCA connectors on both components.
Since you would be doing this just for experimental purposes, before possibly investing in a pair of long RCA cables, IMO there is no reason to go with the expensive Cardas adapters. Their main benefit in comparison with a Neutrik or other inexpensive but reasonably well made adapter, as I alluded to earlier, would IMO be the gold plating the Cardas adapters (or at least some of them) appear to provide on their contact surfaces. And the main benefit of that would be resistance to oxidation and corrosion over time, which is not a factor for your purposes.
IMO. Regards,
-- Al