Custom firmware for PSP-2000 with the TA088v3 and above motherboard and PSP-3000 by the PSPGEN team. Please note that this custom firmware does not work with PSP-1000 and PSP-2000 with the motherboard that is below TA088v3.
@Veho, I still have my GBA SP that I bought from a decade ago. It's been modded to have a clear blue shell, I might go with adding an amplifier to boost the sound cause it's so quiet.
@mthrnite, Personally, in my opinion, I'm not a huge fan of the micros as you're missing out a lot of features, like GB/GBC support and connecting link cables. It's incredibly difficult to repair because the plastic is very fragile and you could easily screw it up if you're not careful.