To the OP, you will do fine with imported ER-40 chucks and collets for use on the lathe. No matter how we hold the work for a first operation turning the work piece will be concentric with the spindle axis so cheaper collets are fine. It is during a second operation, where the work has already been turned and we must hold it accurately that collets really come into play. Here, you can still use lower quality collets but using a good nut is a good idea. It applies more uniform pressure to the collet and will give you all the accuracy the collet is capable of. Rego-Fix, Techniks and ETM all produce good coated nuts and ball bearing nuts that are not all that expensive; they are considered consumables that help accuracy.