why so many gryphon diablo 300 integrated for sale now?

Hit the nail on the head. I have a Diablo 300 and I’m wondering what the Luxman 509 will sound like in my system. 

Thay must be Boat anchors   or    they flood the market    pick one 

I've got one that I absolutely love with its ability to throw absolutely MASSIVE 3D soundscapes, its tight and iron grip bass, and its super fast (but simultaneously liquid and musical) capabilities. I have to admit however that I've gone through thought exercises as to what would trigger selling it as currently funds allow and I've upgraded other aspects of my system such as moving to much larger Magicos - all things that trigger an across the board review of one's system. I have heard the Soulution 511 integrated in a system similar to my own which sounds surprisingly close to the Diablo but it's $32k - roughly $12k more and the Diablo, not as beautiful form factor and on paper the Diablo provides 2x the wattage of the Soulution into a 4 ohm load such as the Magicos. Soulution and Magico are commonly paired at trade shows so that still has me curious as to what it might be like in my own system - but not enough to actually make a move.  One reviewer has said that the Diablo is equivalent to $60k in separates and I have no reason to dispute that - it is a darned fine sounding amp+preamp+phono+DAC (with the optional modules). Currently, however, there are also some damned good individual amplifiers in that $50-60k range now that let's face it - it does get one's curiosity going especially when looking in the context of driving speakers in the near six-figure range. Does it violate some rule of Audiophilia that we should absolutely have separates when a system gets to a certain level? That's the crazy hobby we are in, right? Always second guessing ourselves and psyching ourselves out into trying new things after we've read a review or show report, even if those things are just different and not necessarily an improvement.

I own my Diablo 300 for 2 years now and it still satisfies me to the bone. What a wonderfull amplifier. The only question I have for myself is if I should have bought the DAC module with it. But parting from my Diablo, not likely!!!