Digital Devil Saga is probably good, like everyone else said. If you have a DS, you might like Strange Journey. Since it sounds like you already have access to P3, that's always a good one.
So I'm in Sector Fornax in SJ. I'm so glad I continued this game. It has just the perfect difficulty for a dungeon crawler in my opinion, and the environmentalist story has a perfect combination of religion, philosophy, and psychology to really be effective. That and I like that Black Frost is so useful. I'm a Jack fan.
After SJ, I'm thinking of either going to DDS, Nocturne, or Persona 4 (I'd be Nuzlockeing Persona 4). I really cant wait to get to these though.