Z23 over emphasize on the sub, best to play boom boom boom in big room

so your next target must be upgrade better than M33, the design itself contribute a lot
sats are tilted facing upward --the key of M33 to good clarity
while sub is side-firing slim box (push little air) +lightweight (box vibrate itself) =muddy --avoid this
C3 sats are great! sounded very wide but cannot go loud

S330 got fancy phase plug tweeter +big dustcap, still a 2.5" mid-driver

where C3 mid-driver perform better
of course Xonar U1 can be used with powered speakers, lower down U1 vol & raise spkr vol if you hear distortion.
btw, if you don't mind used stuffs, go check out sales thread.
a lots of goodies which i got from there