I use this box for several months.
Coupled to two dual head 15, it does the job properly and reported a more sacred in the lower frequencies.
What I like most is the power (1200W RMS), however this box is very compact (2x18 ")
It is true that the SP 218 subwoofer is a pricey but the quality is there, it's tough: carpet finish, roulette ...
Used on a carnival float, this is largely sub 1300 W for several hours.
With experience, I'll get the Electro-Voice (EV is famous for) or the Cerwin-Vega <3