Before buying a second set of speakers, consider looking for some high quality speaker stands. Then position your speakers properly away from side and rear walls, if your room would allow it. Add a good subwoofer to fill in the lower register and will experience a and you will experience a lifelike soundstage, with a huge musical presentation that is deep and wide and tall.
If you are eventually going to all Nak look for an amp or receiver that has the 'Stasis' label on it. These are designed by designer Nelson Pass of the famed Threshold and Pass Labs amps. These are Nak's best sounding amps and receivers, and worth the hunt and extra cost for one.