How much do I need to spend to get a preamp that sounds better than no preamp?

kosst. correct, I cannot read a schematic. However, I have trust in my listening abilities, and this far outweighs any scientific hoopla " in my quest " for better sound. You are just plain ignorant, and I have NO RESPECT for you. In fact, I still find you laughable with all of the argumentative outbursts you continue to belt out here, trying to prove something. As george said, " go away ". There are many people here who are scientific, and I enjoy their responses, but the stance you seem to take is always childish. You take the fun out of this hobby. I cannot imagine you sitting in your listening chair, enjoying your music, as it seems all of your leisure time is spent here ranting. I get a good hour or so, daily, enjoying my listening sessions. So, Enjoy ! MrD.

Don't worry  mrdecibel

 I had to have Nelsons view again, so I emailed him, and asked under "ideal conditions" when only the passive (<3o'clock) is used what happens to the active stage, this is what he said again without revealing what the "patent" part of the circuit was.
So as you can read at 3 o'clock and below in volume all you hear is the source.   

" Under ideal conditions, where attenuation of the tap point is exactly that of the active gain, the active stage disappears, and any setting below that is the source.
Non-ideal case would include distortion, which is attenuated by the ratios of the source impedance, potentiometer impedance and load impedance, the active circuit being s current source."

As I said, kosst had a nerve to question what he said, as he isn't Nelson itch spot.

Cheers George

There is no patent part in that circuit that’s not in the service manual. And that’s the problem with your understanding. You’re just making that jazz up. As Pass says, it "disappears". The active gain never shuts off or goes away. Of course the direct signal would become the dominant feature. Certainly not the only one. 

George, I am not worried about a thing. Thank you for your concern. Enjoy !

You right, the best preamp is passive, with no amplification, If you power
amp  get  good gain and speakers get enough sensitivity , Take a look
Alexus preamp