You should do some research online, but the new 509 is a class AB configuration, and the 590 is listed as class A, it’s spec’d at 30W@8ohms, but actually measures nearer 90W. It was Luxman’s top of the line until the new 509 was introduced. Now I’d say they’re both at the top, depending on what you prefer. The newest version is the L-590AX MkII. The earlier L-590AX’s are available used in excellent shape in the low $4000’s. That’s the model I own. Also, and I don’t remember your requirements, but the Luxmans, unlike Accuphase, have a very good phono stage included.
http://www.navratilaudio.cz/novinky/Luxman_L590AXII_HFW.pdf
http://www.navratilaudio.cz/novinky/Luxman_L590AXII_HFW.pdf

