Also,. google impedance (not box/enclosure) rise. Google, read, and take some of that in. I dont know if your going strickly for numbers in the lane, at one frequency, or if your want a daily ground pounder (sound like you want a ground pounder system) but, just looking at "this amplifier does this number at this load" is pretty useless in a daily driven audio rig. That said, it will help explain why your not seeing even remotely close to the power you think you are, or should be. Not to mention, that board/maker, most likely embellished the numbers. I do wish you the best of luck. Hell, just coming in and asking questions, and wanting to know and learn, ... you are already well ahead of most, and the curve. Cheers and best of luck.
edit- also, remember, if your are looking for "large-ish" numbers. It takes power, to make power. No board on the planet can "make" power on its own.
Also,.. please. Please be very very carful, of who you are taking info in from please. There is a TON of nonsense, and welp, straight bullshit out there. Do your own reading and learning mate. Sure take others info in, but be very very carful on what is out there.