Popping when source is switched or muted HUH????

I'm not convinced there is anything wrong with your pre. Did you have the problem before inserting the InnerSounds? Since you haven't mentioned it, I'll assume you aren't using the ESL x-over/amp that mates with the stats? If not, what are you using to crossover to the panels?

I am using the cross over amp and powering the bass with it, and it was doing it before, now it is really pronounced though

If you heard the same pop, but at a lower volume when you used your AR-9's, the level is now louder because the Eros ESL panels are 6-10 dB more efficient. The pop may be intrinsic to your Rotel processor. Be thankful you aren't using ALE or Goto horn systems: at 115 dB/w/m efficiency, the pop would probably sound like dinner theatre night with John Wilkes Booth.

lol thanks Steve!

I have the same problem.I just try to remember to keep the volume all the way down on my tube preamp before selecting
another source.I may call up Conrad Johnson about my PV-5
on this and see what they say.In my case I was wondering if its the tubes going bad in the preamp.