What to expect if I import an amp and preamp from a Japan seller via US eBay

A quality step down transformer will make no audible difference to the sound. But as someone mentioned if the amps are Accuphase it is not difficult to convert to US voltage.  It's the same with some other non US manufacturers.

I would make sure you were dealing with an extremely reputable dealer in Japan, such as Hi-Fi Do from whom I’ve purchased in the past. In retrospect, I would be reluctant to do business with a dealer from Japan, and would find something here in the USA which will satisfy you within your budget. There are just too many things that can go wrong, Including damage from shipping internationally, customs duties, etc., and I don’t think it is worth the risk or the potential headache. Just my two cents based on years of experience,

If Aauphase no step up transformer ,they just change the taps 

my friend bought one this spring the E4000 and sounds great. From eBay 

The seller has a great feedback rating.

carlsbad2

As has been pointed out here by others there are a host of things that can go south when buying an item on ebay from Japan. I have bought and sold on ebay many times and audiogon and us audiomart. Also bought items from Japan, Russia, Japan, Poland and China. Usually bought from a dealer when purchased overseas. Good deals and bad ones. Warranty has not been an issue as much as just reliable quality repairs. I would not want to ship a preamp and amp back to japan. I am glad the OP is thinking about these things.

To me, Esoteric makes great products and would like to add their streaming dac.   The us markup compared to Japan is higher than luxman and accuphase by almost double I am tempted to make the purchase