Do not fret my friend! There is a build of PSP MAME4ALL [v4.9r2] that will run on your 6.60 CFW PSP. The only downside is that it doesn't run CPS1 or Neo-Geo ROMs. No biggie though! Those games run like sh*t on PSP MAME emus anyways. If you wanna run those ROMs well, use CPS1PSP and MVSPSP. Those emus run their respective games pretty dang swell!
So, enjoy your Galagas, Galaxians, Donkey Kongs, and Ms. Pac-Mans! Oh, and this emu also runs arcade Double Dragon, and runs it pretty dang well. You gotta find and use the right ROM though. It's called "Double Dragon (bootleg)". And if I'm not mistaken you'll also need to have the real DD ROM in your ROMs folder for it to run.
This emu runs best on 64MB RAM PSPs, but will also run on 32MB RAM ones, including eCFW Vitas! Oh, and as a bonus, I pimped out the EBOOT graphics, and added some muzak, cause I have fun doing that type of stuff, and I like pimp sh*t.
If you need any help in how to use this thing, or configuring this emu for optimal performance, holla.
Anyways, here's your link of awesomeness!http://filetrip.net/dl?sur70vJboK