diamond may make great stuff, especially the components I've heard them very neutral and smooth sounding (s tweeter). But, about the subs I can't say really.
I am wary of any company though, that boasts this and that great feature, but won't post the T/S specs of their subs anywhere. What further makes me wary is that they do not post the inductance of their subwoofers. Not many manufacturers do this, but I feel that knowing the inductance of the voice coil is an important thing. I can't get the Fs, the Qts even of the subs, so how am I going to model the frequency responses and figure out if I have even enough space?
I know, I know, I'm going to get chewed out because there is no replacement for real world tinkering and trials, but it's just that really accurate modeling and careful attention to the parameters that matter have yielded highly satisfying results for me in the past. When the modeler said it'd play deep, it played deep. When the modeler said that it was going to peak at a certain frequency, it did so, almost precisely.
So, without diamond giving me information in which to base a decision on, I simply have stayed away from them, and being that no retailers around here have any diamond subs set up, what am I to do? I have to resort to people's accounts of things, of many of whom I do not trust their ears or their perception or understanding, or I have to resort to the T/S stats of which I have learned to trust to a certain degree. So, why don't companies make it possible to find detailed stats of their products somewhere on their website?