OK, let me try to answer your question, as I understand it.
I think you are asking about the shape of the cone of the woofer - why does it vary from different manufacturers? Some woofers are concave, others flat. I am not sure why each manufacturer elects to use the shape that they do, though I am sure that they have marketing responses to that query.
I don't know what your current sub is, but I can tell you that building your own sub is fun, and not THAT hard. As Skiguy is having a ball doing his, so could you with yours.
I have built 2 to date. One is for my HT - 12 inch Nakamichi sub in a 4 foot box, tuned to 23Hz - BOOM for movies. The other is a 12 inch Fosgate sub, in a 1.5 sealed box - TUNE for music. Both are driven by my 300w BASH sub amp, fed signal from my integrated amp. Both are CAR subs, presently in use in my home audio system.
Very different sounds, and efficiencies, driven with the same amp - likely because each is carefully optimized in each box, for the sound I was looking for, out of the specs for the driver.
If you want to build your own sub, and have time, and interest (and likely around US$250) you can do so.
Hopefully some of this answers your question,
Mark