D’Agostino Integrateds

it could be due to your interconnect or your speaker wire or both if you're using OFC wire that definitely could be the problem that's the worst wire for audio you could have you should try OCC single crystal wire.

also you might try the Townshend podiums underneath your speakers those things get rid of a lot of problems, the mid b a s s problem could be because the vibrations are going out of the speaker into the floor and back into the speaker again and shaking it causing smearing in the sound stage they're not cheap but best upgrade you'll ever do.