What is the latest PSP firmware?

So the last time I had a PSP was a year ago and just got one recently and currently it has 5.50 gen d-3 but I cant seem to play the new games. I looked around on the Interweb and there seem to be tons of new firmware like Pro, ME and TE and what not. Which is the most stable firmware I should update to and should I update to another firmware before I can update to the chosen firmware?
Answer #1
snip
Any acronym such as lol.
The use of +1…+X within posts.
The use of an emote only reply (such as 😐 )
These are only guidelines not strictly limited to just these examples.
Answer #2
6.39 pro b 8
Answer #3
daxdax89 replied: 6.39 pro b 8
isnt the PRO firmware temporary? I found 6.60 ME and have installed it and it is permanent. Im downloading a game right now see if it works.
Answer #4
ITs perm and it has all plugins enabled.6.60 dont