OP: Fritz typically makes ported, I believe, and they have remarkable low bass extension. My suggestion was just that if you are committed to sub use, sealed integrates a little better, and results in a smaller speaker, so I'd discuss it with him, but no idea if he'd make one. :) I'm sure he's going to call me to complain I suggested this. :)
Alternatively, buy a ported, and consider stuffing the port when using a sub.
Alternatively, buy a ported, and consider stuffing the port when using a sub.