The purpose of DSP is to improve the acoustic signal at your ears, not to preserve the amplifier’s electrical output. If it reduces the far larger errors introduced by the speaker and room, the result is more accurate, not less.
Much better than chucking DSP at a problem caused mostly by poor speaker choice, poor speaker set-up and poor room treatment is surely to do as much to rectify those problems, before deliberately spoiling the amp's nice flat frequency response?