I do not think your current set up has any gain mismatch issues. If you are listening at the 9 or 10 o'clock position, it is okay. I would say you have a problem only if you are always below 8 o'clock.
The factors involved are the output of your digital source, input sensitivity of your preamp and amp, preamp and amp gain and speaker sensitivity.
Please describe what you mean about the loss of sound quality when the preamp -20dB jumper is used. The fact that your unnamed preamp has this feature means it could be modded to other values. You might want to contact the manufacturer.
Your unnamed speaker are not such a tough load unless their impedance varies wildly. They may not be the current monsters you think they are.
The factors involved are the output of your digital source, input sensitivity of your preamp and amp, preamp and amp gain and speaker sensitivity.
Please describe what you mean about the loss of sound quality when the preamp -20dB jumper is used. The fact that your unnamed preamp has this feature means it could be modded to other values. You might want to contact the manufacturer.
Your unnamed speaker are not such a tough load unless their impedance varies wildly. They may not be the current monsters you think they are.