I too use find-DVD.
I buy from numerous on-line retailers, don't just stick to one, as I try and get the best price.
I buy both region 1 and 2, which find-DVD searches for. Can't say I use Play or PlayUSA more than others as I don't as they aren't always the cheapest, neither are Amazon, it all depenRAB on the individual title, I'm not loyal to any retailer.
I have bought region 3 and 4 which I use other means of locating the film I want.