^^^
For that above post, I looked at the FV18 and the FV15HP compared to the two newer Monolith Subs, respectively the 16 and 13.
Between Data Bass for the Rythmik Subs and Shady for Monolith, these Subs are almost identical in performance.
Perhaps the most telling aspect is in the Long Term Compression Sweeps which seem to favor Rythmik... But it is close. I think Mono wins in distortion, iirc.
Ultimately it felt like a toss up.
I would probably choose the 13 over the 15HP, but the FV18 over the Mono 16... Unless there is a sale. Then all bets are off and the loweste price wins!