When considering using a passive line stage one should also consider the output voltage of the source components and the input sensitivity of the amplifiers. While the CD standard output via RCA is 2 Volts and the HDCD standard output via RCA is 2.2 Volts, many don't play be the rules. Some are over and some are under. Other perhaps considered legacy components such as tuners, tape decks, etc., are often well below (and less likely above) and might not be able to drive amplifiers to the full power output that the consumer paid for.
