REL Strata III repair issue

Thanks all for your responses.  Update:

I now have the Strata in a secondary system using an inexpensive outboard amp/xover (NHT).  Getting pretty good (not great) results and the jury is still out on the fate of this Strata.  

Dave, thanks for your thoughts; I will have a local tech check the defective amp module.  Further update:

I have bought a pair of REL Storm III subs as I have always wanted to try stereo subs.  Well, everything they say about stereo subs is true: smoother, less lumpy bass, improved dimensionality and absolutely huge soundstage among other benefits.  So far, I am very pleased with the results, but am trying to diagnose a potential problem with one of the subs.  Although there is no sign of distortion or strange sounds of any kind, one of the subs gives noticeably less output (or has lower input sensitivity) than the other.  For the same level of output that one sub provides with the volume knob at the 2/3-3/4 mark, the other needs to be almost maxed out.  I plan on swapping out the amp modules to make sure that the issue is not with the speaker itself as opposed to the amp module.  I contacted REL about this and they tell me that as long as the sub provides  undistorted sound that there is nothing that they can do; it either works or it doesn't !?!? Thoughts?

Interesting that you should experience the same issue, Dave.  My two subs came from different sellers and from a cursory examination of the modules it is obvious that, while they are the same design, they are of different vintages.  I removed the modules shortly after receiving them and was able to compare, but didn't swap them at the time as I wanted to first have a better sense of what was happening sonically with each.  I do find it strange that, even if the one that gives less output, is operating "normally" and the difference was a deliberate design change, that it would mean that the volume would have to be almost maxed out in the context of a system that is pretty conventional.  My Manley tube monos currently drive a pair of fairly easy to drive and efficient transmission-line Paragon Regents.  Is it possible that since the Paragons don't need much power to get them going, that the RELs then don't see sufficient current; hence the need to turn the volume way up with the High level input?  Like you, my ears tell me that the xover frequency selector switches are calibrated differently in each sub.  This does affect the perceived output; still.....,  I also think that, while subtle, the lower output sub's sound has slightly less impact and definition.

Fantastic information, Ken.  Your description of the sound quality of the suspicious sub is exactly what I hear: "rubbery/boomy"; BUT, from the less loud sub.  I will take a look at the wiring and see if I can find some inconsistency in the wiring.  I'll report back.