You can adjust the saturation of colors once converted into black and white, so the color is irrelevant.
All you need is photoshop or lightroom. Plugins are a waste of money in my opinion. I have silver efex pro 2, and once I learned how to adjust B&W in photoshop I never used silver again.
I do a lot of black and white photography, but I never imagine what the image will look like in black and white. Some people claim they can do that, but I can't so I let the image dictate the type of black and white post processing.
Some of my images are heavy in contrast, others lack both contrast and texture. But a black and white image does not have to be one or the other to look good.