Great to hear of your progress!
I use a COSEL P100E-5-N 5vdc 20 amp power supply that I bought on ebay for only $20. It's a cage type open style supply but I could not beat the 20 amp capacity at 5 vdc as I thought it would be very useful for my projects. A panel of these displays
If your power supply is getting too hot, then it probably is overdriving it for current. It may shut down the regulator temporarily if this happens.
The 6 amps you are drawing makes sense as the data sheet states they have a working consumption of 30 watts. So using 5 vdc this means the working current draw is (I = P/E = 30w/5v = 6 amps).
Remember these mount in a cabinet of 24 of these displays which have I beleive (4) 5vdc power supplies AND - many cabinets of 24 (at 350 watts average = 70 amps) are used in a large outdoor screen of maybe 8 or many more cabinets - So hundreds of amps can be used in an outdoor large RGB display.
I love the brightness too - but your only talking about a 16x8 RRGB resolution - so many more need to be added and through SPI, fast display data can be displayed.