PSP Brite (300X) 9th PSP generation · Pandora Battery access: No · Downgrading possible: Yes · lowest Firmware: 6.30 (6.20) · Permanent CFW patch available: Yes

From here you'll have different options to choose from:

Option 1: Install a permanent patchable 6.61 Custom Firmware via Infinity (with small brick risk)

Option 2: Install a temporary Custom Firmware (needs to be reactivated after reboot, no brick risk)

Note: You might consider installing a 6.60 CFW since most plugins,
themes and programms are not optimized for 6.61 as of yet!

Note: This PSP Model is not intended to run any lower firmware than 6.30!

Downgrading this model to 6.20 will make the PSP unstable and cause some functions to be broken!!
Therefore downgrading is not recommended but possible!!