Luxman L 505 U Integrated Amplifier

I've had the L-550 Mk2. You're right it probably is a step up from the L505u, but keep in mind that it is rated at only 20watts X 2 in pure class A. although, it is very much underated and probably puts out more like 65 watts X 2. nonetheless the L505u has more power (100watts x 2). Something to keep in mind when matching these amsp with speakers.

Waiting for my 509u, I tried the 20wpc pure class A 550AII with my B&W 803D.
It was clearly not enough for my speakers (good only at late night volumes) but I heard it with smaller and more efficient speakers (Living Voice) in my dealer's showroom and it sounded very well, very musical.

Luxman class AB (505u,507u and 509u) are different from class A integrated amps (550AII and 590AII).

Don't expect from a pure class A i.a. great control at louder volumes driving difficult speakers with rock or classical music, great detail and absolute neutrality.

On the other hand you can't ask 509u the warmness and musicality of the 590AII.

Luxman, that's to say, demonstrated both 509u and 590AII at Tokio International Audio Show with B&W 802D speakers, even if it's clear that 509 has better driving capability.

You mean Step Down rather than Step Up (USA 120v to 100v) for the Japan version of the L505 right?

I purchased a Luxman L505uxg direct from Japan. No pangs of guilt here as it relates to the US Importer. Saved $1200. No import duties were applied. Purchased a quality Acupwr 1000 watt US made step down transformer. Absolutely no impact using the transformer relating to sound quality. Transformer runs barely warm to the touch. Couldn't be happier.
Consider the lack of a US warranty a risk I was willing to take.