How much gamestop store credit can I get for these games? Would it be enough for a used ps3?

I think you have enough. I sold my ps2, and like 35 other games for it also my 360. For the ps2 i got $35 for it, $4 to $10 for the games but $12 for Final Fantasy XII (I don't know why). And for the controllers they were like 5 bucks. Well since you have 190 and are selling your ps2 stuff I think it should be enough for a used one if not enough for a new one