I think the short answer is that if you enjoy the Silks with the grills off, you'll like them with the grills on. As Jim points out, you can see the impact of grills in measurements. But most of this is caused by reflections off of the grill frame members. Those have far less sonic impact than dips and peaks that are inherent in driver response or crossover implementation. Just play out a little mind experiment. If you place two vertical wood dowels to each side of a speaker and measure, you will see a disturbance in the response. But do you really think you would hear that? If your eyes were closed, do you think you would be able to tell whether the dowels were there or not? I doubt it. To the extent that the grill cloth absorbs some high frequencies, there might be a slight softening in the sound. But compared with all of the other ways things can go wrong in speaker design, this is a really minor issue.