I'd recommend that you download rebug 4.80.1 and install the newest multiman and reactPSN. You can download official PS1 games via psnstuff iirc and multiman has a feature that allows you to load CD and BIN/CUE based PS1 games but I think theres a program that allows them to be installed like packages called PS1 to PS3 GUI or something like that. The PSP has a converter program like that too oif you wanna play some PSP games on the big screen.
For games downloaded from psnstuff you download the pkg of whatever digital game you want and the rap file from the application and put the pkg on a usb or transfer it to your PS3 via ftp. Then you wanna put a usb stick with the rap files in an "exdata" folder in the rightmost usb port on your PS3 and create a new user named "aa". Run reactpsn and it will use the .rap files to fake ownership of the games and make them playable on your PS3.