Oh okay, I'll take your advice and give it a go then. Thanks!
(Just finished setting it up: Note to others - install Retroarch 1.3 on your PSP. 1.3.6 crashes with Gambatte (and I'm not the only one, bug report is in the repo).)
I'm waiting for new headphones so can't really test yet, but it's running now at least, plus I can play with Retroarch filters!
Anyway, I finally found where Retroarch puts its saves, but noticed they're in .srm format (as opposed to the .sav format in RIN). Is there any way to get .savs that I've downloaded from the web/bandcamp/etc. into Retroarch?