Your room is 50% of the sound of your hifi. your speakers probably 40% and the rest of the hifi the last 10%. Sort out the room before dicking about with cables and swapping gear. Your speakers and amp will both go out to 20khz, but your room will soak up HF its it's heavily damped with soft furnishings. Twiddle about with listening on and slightly off axis, crossing speakers in front of listening position etc.
Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m