OP -- you should consider the 550 and 590 models as well. They are quite similar to 507/509, but IMO add a bit more warmth and texture to the sound owing to their ability to operate in pure class A further than the other models.
Luxman 507/509
I wonder if anyone out there can answer a question I cant find an answer to anywhere on the internet please? I have the option of a good deal on a Luxman 509x but clearly still a fair bit more than a new 507uxII. I honestly cant convince myself of a difference in sound driving dynaudio heritage specials but I wondered what technical differences actually exist between the two - aside from a modest difference in rated power output. Any thoughts? Many thanks