Just get the one you want. I have had great success with AQ products in my current car. I have heard the HDC3 18s more than enough times to know that they are some kick *** subs. Great build quality and performance despite what some may think.
But me being me, and having 2 cars after tomorrow, I will strongly consider doing an all Sundown substage in that car. 3000D on either 2 15 NS or one 18 NS.
The OP says he makes 100K+ a year so I don't think pricing is a real issue.