1) Speaker placement
2) Amp
3) Preamp
4) Speakers
5) DAC
and room treatments.
Very few speaker models have been intentionally designed to be placed against a wall, but most "audiophile" speakers should not be against the back wall - should be pulled into the room and then moved trial n error (including toe-in) until sonically satisfied.
If you are unable to move your speakers into a satisfying sonic location, then perhaps a nearfield or a desktop system would be better sonic choices.