Atomic Loudspeaker is SJA..... They build for RD Audio and American Bass VFL and VFL Extreme.. Now that Resonant Engineering was bought out by U.S. Amps, they are no longer going to build O.E.M. products for other companies as far as I know. They are also moving from Vegas to California... TC Sounds (which was way over priced on O.E.M. items) is out from what I understand and Dan does designs only, and I don't know of him building anything right now. The only build house (for car audio that is good) is Easton.
Eminence is still around but only do small subwoofers and more home audio and guitar subwoofers. They used to build the entry level stuff for Adire. Credence is another build house but, it is nothing really special.
I know Nick at IA does O.E.M. items and some has the final assembly done in the U.S. and most comes from China. I do know of a new build house that can get parts from both the U.S. and China but, I am not going to post the information here and I know they can help you with amplifiers too. Send me a p.m. and I will see if I can help you.