Keychron Q1 is the best custom keyboard you can get for under $150 but there are some issues to work around. I think this has better value than GMMK Pro.
https://www.keychron.com/products/keychron-q1

Additional Notes:
I used 3mm thick PE Foam on the BOTTOM of case.
Tape on the bottom also gave it a deeper/lower freq. sound but I don't love it.
I tried 2mm PE foam up top, didn't change the higher pitched ping much. It also made it sound like every other PE foam mod.

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