Psp go with ofw 6.20?

I just bought a psp go with ofw 6.20 from a friend of mine. I want to be able to play copied iso's and the eboot games I download but the games news 6.31 or newer. My question is what cfw can I download for the psp go that will play iso's and the eboot games that I have saved to my PSP/GAMES folder on my psp go. Only thing I really know is that it's a psp go psp -n1001 and it has official firmware 6.20. Any info would be great. There are so many out there that I'm not sure what to use for these specific needs. I do want the xmb feature btw.