Difference between Luxman L-550A II & L-507u


I was wondering if anyone has heard both of these Luxman integrated amps, and can comment on the sonic differences. I have heard the L-550A II and the bigger 590 and was very impressed. I'm seriously considering getting the 550, but just read about the 507 and am curious. It's not on audition close to me, so wondering if anyone can chime in (and not just a guess about Class A vs. Class AB, but actual experience).

Thanks!
brookjoo
Anyone hear or try the 550A with the Harbeth M-40.1's? I'm thinking a 20WPC integrated, albeit conservatively rated, would have a tough time pushing 40.1's 12" woofers.
Thanks Brookjo for your comprehensive review about the difference between the Luxman L550 and the Luxman L505u.

Within a few weeks I am going to buy one of these. Mainly I listen to classical music, especially organ, but also classical works with vocal solists, sopranos in particular.
So far I think I go for the L550a.

You'd helped me with the review. Thanks again.
Please tell me when you have any tips for purchasing one of these aplifiers, concerning other reviews, warnings or recommendations. Peter Roek (The Netherlands)