Marty, you should look up the jbl w15gti sub, it will do very well up to 300hz and can get down below 20hz , but to employ that low and that high, the balance may be off. Too much low end will sound very muddy, and male voice sound out of balance.
Once it gets to 1000/speaker, I think it would move 10 piece a year the 1st few years and less after that. The finishing are a important factor once the price gets up high. He should sell complete speaker for reference. 2000 a piece is reasonable for a finished seos ref. whatever that may be.