There is very little that the fancy "long range" muzzleloader being offered can do that your Black Diamond can not match. I would save my money and buy more bullets and powder. I also have a Black Diamond XR and they are an excellent shooting rifle. I do not know of any rifle that could shoot better once you have the right load.

As for your powder charge, do not be in a big hurry to shoot 150 grains. Most of the rifles that shoot those large charges get terrible accuracy and they end up shooting 100 grains which is the same thing you do. Your powder charge is all you will need to get the job done. If it ain't broke, don't fix it.....