I have a strong impression that I saw a table where there 3.2 Ohm was in a column for Ultra, but not for Select. I just spent 15 minutes trying to find anything on the subject to no avail (I remember it had taken me quite a bit of effort the first time).
So I would say that, until I find it again, let's assume they both have the same tests for what I think they called "amp stability". If I ever fall on my original info again, I will enquire further and report back (but I do not intend to spend any more time on it!
).
