Do u want a latest custom firmware or original firmware?
Ok if u the latest and original firmware, then OFW 6.39 is for u.
However if u are looking for the latest cfw, use 6.39 ME-8 or 6.20/35/39 PRO B8 depending on ur PSP 2000 motherboard. If u have a hackable 2000, then you should try ME-8 however if ur have a later motherboard, then use PRO B8.
What's ur firmware now?