M700 upper midrange hardness and run-in period help please

The M700 has gone through more than 2,000hrs as I always leave it on stand-by mode after listening session. Running in the amp helps rounding off the rough edges a little but the root of the upper midrange hardness problem is from my Benchmark DAC1HDR. Have since replaced it with the Border Patrol DAC SE. Much more body and sweetness in the midrange now. The M700 is a rather neutral sounding amp. Need to be careful with front-end hardware if your speakers are also revealing type.