Eesh. More than I remembered. I forgot I had priced everything out when i was shopping and realized it wouldn't be much savings over just buying from HSU.
Sonotube might be the way to go. Cylinders look cool too and the shape is inherently stiffer for subs.
*Edit: The NX3000D is the amp I got with that RBH sub!
Yes.
The Hsu VTF 2 is still one of the best buys in Subwoofage, bang-for-the-buck style... Regardless, $609 ea +$95 S/H for the single unit.
I am at a loss to really offer a better solution, new, OEM vs DIY.
Money could be saved on Raw Drivers, but at what cost to the final product? Higher distortion, questionable performance? But their are less expensive ones, and an NU3000DSP on the used market if OP is lucky... ???
*shrugs
Again, Bang For The Buck.
If he builds these well, they are foundational Subs that he can use for 10years+. Same with a new Hsu.
Another option is if he can find a deal on the preferred JBL 12" Drivers, he could build a Boss Platform for very little money. Amplification would still be the kicker.
Beyond thata, NEW, the Sub 1200 is likely the best option. Otherwise its old used subs and fartboxes at the whim of his local CL or FB Marketplace.
*shrugs