No, I do not have experience with Japan Buy. Understand that anything meant for the use in the Japanese market will need an AC converter to work in the US. Easy to accomplish, but a caveat to be aware of.
There is good value to be found through importing directly from Japan- lots of great equipment to be found. HiFiDo is an old and reputable seller of used equipment. I would have no problem buying from them, and in fact I monitor their site regularly because I am looking for a specific phono cartridge.
Triode equipment is designed in Japan, but made in China by the parent company of Line Magnetic. I point this out as fact, not as criticism. I own a TRV 845SE, and I am very happy with it. I don't think Triode has a US distributer now, so I think they would be wiling to help in the event of a problem, but honoring a warranty may be problematic.
Have you considered a Cary 805c ? 300B driving an 845 for 50w of SET glory. Seeing them on the market for about half the price of the TRX M845....