for DVD sets i would probably recommend either DVDboxoffice or DVDsoon, neither get hit by customs very often if at all.
DVDsoon seem to mark every item in the order at $12 value.
My normaly tip is to look at the price of the DVD's including any shipping.
If a retailer is 20% cheaper than DVDboxoffice after allowing for shipping i'll normally risk them.
If not and they are a company that do get hit for customs a lot (Amazon are awful for customs), then i go with DVDBoxoffice.
One word of warning, once you start getting into anime DVD's you'll probably regret it when you look at your bank balance
Most ADV disk 1 + box are not really that limited.
Most Bandai disk 1 + box's are limited in some form, usually to about 10 or 15k
Almost all Pioneer/Geonom Disk 1 +box are limited, but they don't always say so at the time (examples are Ai Yori Aoshi and Amazing Nurse Nanako neither was announced as a LE and it was only realised after initial stocks started running out).
Almost all "digipacks" and "brick packs" are "unlimited", although some will have an extra for early buyers (something like a signed poster).
Apart from that they are normally standard stock items (things like the Evangelion, Nadesico and Bubblegeum Crisis 2040 Perfect Collections, and the Outlaw Start set).