there are loads of adaptors available and i am sure theres not much in it sonically , personally i prefer to have the proper connector though . they are very cheap to buy with correct plug
I would never buy a S/PDIF coax that is terminated to RCA's. It cannot be done cleanly without creating a big impedance discontinuity. You are better off to get BNC's and add 75 ohm RCA adapters.Steve N.Empirical Audio