LUXMAN L509X VS M700/C700U

 I had the 509X, and it is stunning, best integrated i’ve ever heard by a wide margin; The 509X does not have the C-900U preamp. It might have a few bits here and there, but make no mistake, it is NOT a C900u; that being said the 509X is amazing and from what I have heard from a few dealers, the preamp section in the 509X is newer than the stand alone C700 pre; (Correct me if i’m wrong); Perhaps if you want to simplify and just want to enjoy amazing sound reproduction go for the 509X and call it a day; either way you can’t go wrong. One more thing, the sensitivity of your speakers implies a good match for the powerful 509X (I used it on my 4 ohm Dynaudio Contour 60’s and it was enough power there).

So, we know this:
Luxman underrated the 590 in a way they have not underrated the 509 or 507. That is, the measured performance of the 509/507 are much closer to published spec.

We don't know why.

I only offer a hypothesis, that the heat sinks can't get the amp past the FTC.

I don't think this is bad, by the way. It is a smart compromise.

I just spoke to my dealer in upstate NY 
He Currently does not have the cl 38 uc but says it’s his all time favorite 
I will audition the 509x soon 

Half the time that I say I’m done posting, I eat my words. Oh well.
Erik, Luxman’s published power specs are confined to the Class A pieces, from what I’ve seen. The 505/07/09 are all A/B, and specified in a straight forward manner. The L-550 and L-590, both Class A, (but later switch to A/B), but only are specified as Class A.
I looked around a little to be sure, this is Stereophile’s review of the now-discontinued M-800A power amp. Also a Class A piece. I’ll not say anything else other than you may find John Atkinson’s measurements interesting. Luxman obviously has reasons for what they do. I don’t know what they are. From what I have seen, the ratings are the same for the non-U.S. models.
https://www.stereophile.com/solidpoweramps/1108lux/index.html

Erik, Luxman’s published power specs are confined to the Class A pieces, from what I’ve seen. The 505/07/09 are all A/B, and specified in a straight forward manner. The L-550 and L-590, both Class A, (but later switch to A/B), but only are specified as Class A.

So, your inference is good, but my inference is not, based on what?

Your hypothesis is not implausible, but how would a neutral third party judge between the two of us?