Well cheap compared to all the monster amps out there
So correctly done, one would do the Uberamp2-Raal edition, which results in something really big,heavy and lot of heat. And a custom and large chassis, and a pile of $$$
This is a bit cheaper and easy enough for just about anyone to do.
From the Ti Opa541 datasheet, showing paralled opamps good for at least 7 amps rms of output into anything including a dead short...
Designed to be mounted directly to the heatsink, amp board right angle to the heatsink. All wires to the board directly soldered, 4 oz copper highly recommended.
Power supplies are a minimum of 24V at 10 amps, like this, but more current not a bad thing. You need a pair of these!
https://www.mouser.com/ProductDetail/MEAN-WELL/UHP-350-24?qs=YCa%2FAAYMW011AuZKubw9Sw%3D%3D
So by the time you get done, about $400 in parts. Better than spending $4500 on an unknown made in croatia thing with inside pictures deliberately hidden.
.02uf is a film cap, 10uf are mlcc caps, .1 ohm resistors are caddock
https://www.mouser.com/ProductDetail/Caddock/MP930-010-1?qs=%2Fha2pyFaduhEz86YdyVUnzk8BCJOExJuzQrioCIidHi6TdsKxEEAVg%3D%3D
raalopamp - CADCAM.ZIP