Should I change which custom firmware i have on it to a better option? if so, which firmware and why? (what's the difference between LME/ME and PRO CFWs?)
Nop, you are on the latest custom firmware available, and the more stable in my opinion.
Also now that Infinity 6.61 exists, would a PSP 3000 or PSP Go be considered an upgrade to what i have now (better/faster emulation)? Cen it be on the latest OFW and still install CFW or does it have to be a certain OFW or lower to get CFW on it? (PSP 3000/PSP Go specifically)
Yes, Psp slims and go, have 64mb of ram, comparing to the fat version you have, the emulation changs by a little bit, specially on mid-end consoles, like the snes with the spcecial chips running.
I don't want to go as far as a Vita yet (still too expensive for me for tinkering) and the E1000 isn't an option.
Dont go for it, emulation and homebrew its still a baby on it, if you are looking to play at full speed, go for a psp 3000, 200 or a go. [My favorite.]
99% of my usage of this device would be to emulate NES/SMS thru (maybe) N64 as well as PS1 and I don't use any UMDs.
Nes and SMS, run excelent on the psp 1000, as well as the PS1, but with the n64, the device almost die, on any console from the psp series :/*, the emulator was never finished and only some games became playable, aka mario 64, and mario kart, tough none of them are perfect.
I would want it to be a permanently patch-able device since i don't use it frequently enough to keep it in standby between uses.
Any psp can be patched permanently, even psp2000, go and the other, they just need the right firmware to be patched.
Also, what's the best resource these days for downloading the emulators (if not here on FileTrip)?
Wololo, and digiex for english users.
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And as for your emulator choices, these are the best ones, in my opinion:
Game Boy Advance - Unofficial Gpsp Kai
Super Nintendo - Snes9xtyl Mecm
Sega Master System - Sms Plus Psp
NeoGeo Pocket - Race Psp
Nintendo - Nesterj Aoex
Nintendo 64 - Daedalusx64
DOS - DosBox Psp
Neogeo - Unofficial Mvspsp