I recently moved back to using solid-state integrated and was fortunate enough to have a larger budget ($5k - $10k) during my selection process.
There is a guy down in New Zealand who did some pretty thorough listening to a lot of powerful / high-end integrated amps (Gamut, Gryphon, Plinius, etc). He eventually settled on the Gryphon Diablo.
For my own search, I had to go on the "house sound" that I was aware of for each of the brands I was entertaining (Gryphon, Pass, Gamut, Accuphase, etc), because auditioning was not always an option.
I eventually settled on the Gryphon Diablo also. I decided against Accuphase because there are too many gray-market Accuphase products on the used market. The Gryphon gear is hard to find on the user market too (especially the American used market), but after about 4-5 months of looking I was able to find a new Gryphon Diablo, that was used only as a demo in a showroom and at shows, and strike a good deal.
To be honest, I might have jumped at the chance for the Gamut or Pass first, but having a phono stage in the integrated was a big deal for me. Not many of the really high-end integrated amps have phono stages. The Gryphon Diablo does (as an option), and so do the Dartzeel, but the Dart was wayyy out of my price-range on the used market.
It sounds like one of the biggest criteria for you is having the power to drive those MBL speakers. I think the Diablo would do it (800 watts down to 2 ohms). However, like somebody said a bit earlier, you may want even more power than that. Even if you did like the Accuphase sound better than Gryphon, I still dont think the Accuphase integrateds would be able to really meet the true power needs of the MBLs.
Is there an integrated amp out there that even dishes out 1000 watts? Maybe that big Krell FBI (unfortunately, I dont know the stats off-hand)?
Personally, I'm incredibly happy with the Gryphon Diablo. It sounds great, the ergonomics are nice, it looks cool, the price was right on the used market, it meets my phono-stage requirement (with aplomb, btw), and it comes from a very reputable company that has been around for a long time that is known for their no-compromise style of engineering and highly-regulated manufacturing process with strong quality-control.
In summary, if I were you, I would go with Gryphon. You'd probably be very happy with the Accuphase at low-levels, but I dont think it could hang with the MBLs when at a higher volume.
But with all of this said, you may want to look for an even more powerful integrated. There are not many out there that are more powerful than the Gryphon Diablo, but there are some.
Good luck.