Dual 8" woofers has less surface area than a 12". 3 8" woofers has less surface area than a 15".
I'll take a 400watt 12" SVS over any dual or triple 8" any day. 150 watt dual 8" isn't going to keep up with a well designed 12" like SVS PB12 NSD, HSU VTF3 MK4.
Surface area isn't everything either, port tuning, cabinet volume, driver excursion capabilities.
I also wouldn't call a 300watt triple 8 ONE of the most powerful, unless you discard a great many other subwoofers. Seaton, SVS, HSU, Rythmik, JTR, Power Sound, Danley.