Thank you OP for contributing with your experiment. Blind testing, spl matching, as well as adding other opinions, particularly non-audiophiles, into the test is the best way to really figure things out.
I was also in the pre amp isn't important camp for years until very recently. I've heard enough good systems that have used integrated amps or even gone direct from the source to the amplifier that made me question their value. I'd love to go back to some of those systems today and slip in a tube pre just to see what might happen. Aside from volume control and input switching, the pre seems to shape the sound. Tone, soundstage and imaging are greatly influenced by the pre section. With a single component switch, a system can go from sounding somewhat dull and lifeless to realistic and holographic. They can be well worth the investment.
I was also in the pre amp isn't important camp for years until very recently. I've heard enough good systems that have used integrated amps or even gone direct from the source to the amplifier that made me question their value. I'd love to go back to some of those systems today and slip in a tube pre just to see what might happen. Aside from volume control and input switching, the pre seems to shape the sound. Tone, soundstage and imaging are greatly influenced by the pre section. With a single component switch, a system can go from sounding somewhat dull and lifeless to realistic and holographic. They can be well worth the investment.