Depends on what you want them for, but I would definitely get 3DWS, I just got it and it's great
. If you do get 3DWS, then DarkLights is pretty pointless, unless your looking for some real time lights with your game. The first version of TreeMagik is free, so depending on the quality of the models you want, you can just get that. And theres a bunch of shaders in the "Ultimate Shader pack" for free, so unless there's something specific in DarkShader and not included in there, I wouldn't get it
. So I'd definitely get 3DWS, and either DarkAI or TreeMagik, depending on which you want more
. Just my opinion.