The onestop adds a small value for handling then resells it to the small retailers. This inflated minimum order is to force the little guy to order all his products from the onestop and thus you have its name. The other distributors usually allow any minimum but have a penalty in the shipping if under a certain amount. Most distributors I deal with are quite reasonable but they have their problems. The biggest problem is keeping the place stocked with all the CD's.
Early music is really at the bottom of the priority list.
A good distributor is Harmonia Mundi, the others are less than perfect. They include Qualiton, Allegro and Naxos. Albany seems like a good place but we do not order a lot from them. We could list them but the big label new release catalogs are difficult to obtain. Quite often I have asked them to be sent out but after one or two they are discontinued.