Your tank is looking really nice Sundragon. That tiger lotus looks terrific.
And so do the tiger barbs by the way. I have always liked them but since I keep angels it is not to be for me. I am curious why your list for more fish does not include increasing that school.
As for the discus idea, I would have to vote no for this tank. It would completely upset everything that is working just right here; keep the idea for a larger tank. It IS a good idea, just not for this tank.
Keep the pictures coming!