Logitech z5500 bass test spl meter subwoofer upgrade

i&tested z5500 with this bm audio sub wired at 6.8 ohms dc (stock z5500 driver is 6.7 ohms dc) becouse it has wayy bigger motor, more motor force wich makes it little bit more efficient, has also 2.5 inch coil instead of that small 1.5 or 1.75 inch vc. stock amp, will get more z5500&later gonna order some irs2092s amp and power it from 2 logitech transformers wired in series (stock center taps are not gonna be used)