This is one crazy cool subwoofer amp. I used it with Gallo Reference 3 speakers, powering the second voice coil on the woofers, but it can be used with any passive low range speaker.
What makes it so neat is that it has features to change the phase (not just invert it, but move it by an amount) change the cutoff frequency, increase the boost. It basically turns any woofer into a subwoofer.
And it's stereo. It's just crazy cool. I said that already. 2x250w at 4 ohms. I think it might also be bridgeable, specs say 650w at 4 ohms. https://www.anthonygallo.co.uk/pages/products-reference-amp.php
Sorry, the photos are on their end. You can read more at https://www.audioasylum.com/reviews/Speakers/Gallo-Acoustics/Reference3-SA-Amplifier/speakers/211152.html
Thanks for looking,