Effectively, this is a nice amp for low powered subs (what I am using it for). With a 4ohm dual coil subwoofer that gets max 600w, this amp is perfect for that situation, and what I recommend it for — in general. If you can find two single coil 4 ohm subs that both each take 300w RMS, then this will also be perfect for that setup, though I don’t know off the top of my head of a subwoofer that meets those specs.
The reason I choose to use 2 ohm here instead of 1 ohm (where you get the maximum power), is because of the distortion and heat output from the amp at that level. At 2ohm (where it pushes out ~550w RMS), it stays fairly cool and has little distortion The latter means the sound is quite good with a moderate subwoofer.
Overall build quality at least appears to be solid (solid metal all around). Haven’t had any problems with overheating or bad sound quality. Though take into account I only powered one subwoofer with this and no additional speakers.
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A solid amp for low powered sub setups. If you want to power higher end subs that require more output, this amp would not be recommended for you. Specifically stick to a single 4 ohm, dual coil sub that maxes at 700w RMS or below and you will be fine.