The "correct way" to handle this would be to run a balanced line signal to a remote amplifier. That would minimize losses and noise. But you would need balanced preamp and balanced amplifier, or balanced / SE conversion methods at each end.
But since you like the way it sounds now, stick with it.
The disadvantage to running long speaker cables is the high resistance will ruin the amps ability to control the speaker. A Bryston amp due to the high feedback has extremely low output impedance which means "grip" on the speaker, for good detail and bass slam. The resistance from the speaker cable is added to the amp's output impedance which makes the output impedance much higher and the grip on the speakers is reduced.
Putting it in context, the resistance of 14ga stranded copper wire is about 2.5 ohms /1000ft. That is .19 ohms per 75 feet. Multiply x 2 for the return wire and you have .4 ohms added to the amp's .01 or less, call it .45 ohms output impedance. That's still lower than ANY high end, high power tube amp with 8 feet of any speaker cable.
If you wanted to go crazy, you could upgrade to
10ga stranded wire would get you down to 1ohm/1000 or .15ohms. Some solid state amplifiers with minimal feedback have higher output impedance than that and they are well loved.
Rich