I just sold my WSM 22 and replaced it with an offset smoker. I read many posts from people going the other way though so don't think of it as an upgrade so much as a learning experience. They are different cookers and both have pros and cons.
If you have space for both then I recommend that you keep your WSM and add an offset smoker to your arsenal. I love my offset smoker but it is not a set it and forget it type of cooker like the WSM. I miss having my WSM in that regard.
However, I absolutely love the flavor I get when cooking solely with wood. Not everyone can taste the difference but to me I think it has a cleaner flavor and the extra effort required to cook on an offset cooker is worth it.
Given your budget, you will have to search for a used pit to get something from the builders you mentioned. There are other pit makers out there that will fit your budget though.