I used two since January 2013 has coupled S115Mk2 Audiofocus
Amplified by a QSC RMX5050 (before going on the FP6400)
This is an impressive box! A powerful and dynamic bass!
The default I would say the weight (90kg) and size! but it's still the lightest in its class!
I've tested different subs: PX2181 EV - EV TX2181 - LAcoustic SB218 - Nexo RS18 and Alpha S2! on the other hand out of the question to compare it with subs Chinese import company and brand! It is a pro product!
Simply: The top view is Audiofocus equivalent of two models (and again) only the rate is approximately twice besides the amps and necessary to its products fonctionements processors rack! While ... a processor and a setting and ca roll!
For value for money: Simply unmatched! A great product made in Europe!