Rel is a realistic person. The fault with the source theory, which harks back to Ivor the Invincible, is that not each link in the chain is equal. By far the hardest components to design and build are speakers. Ivor was right, in a way, an analogue front-end being at its core a transducer, it is also quite prone to various ailments, so, for analogue fans, improving that part of the system yields appreciable results. Why no one tests systems as a whole still baffles me, since no one yet has been able to listen to a power amplifier without a source on one end and speakers on the other. Check out the archives, this, like most other metaphysical audio subjects, has often been discussed on this site.