Is there a big difference in sound the gold vs the reactor 900?

[ogs]

Gold is a three way speaker with a mid range driver. Reactor is a two way design where much of the lower mids comes from the bass drivers. Even if one has equal sound level from a Gold and a Reactor in a stereo set up, the two would sound very different. You might do a little better if you used something like Dirac or Audiolense (or one of the other solutions) to correct the odd pair, but the result will never be as good as two identical speakers in a stereo setup.
Another thing is you'd have some difficulties getting only L to one side and only R to the other.