In my opinion as a wheelwhore ...best place to shop is to try and buy 2nd hand locally...next best bet is to go thru a trader even though it costs a little extra, you get the peace of mind that all customs, duties and freight is calculated for you and you only pay the price quoted by the trader...no additional surprises..
If you buy direct from Japan you will need to either have a good mate over there to package everything and send it over..then wait for customs to sting you for the extra...that said, your freight options are limited to container (if you can find one) or EMS (Bloody expensive)
I've bought half a dozen sets from traders...the only downside is the 6-8 week wait. Fun part is shopping on yahoo auctions...find exactly what you want, get the trader to quote and bid for you...pay the $$ and wait.
If you want a reputable trader for wheels, contact mxfly on ns.com.