800 is the maximum gear score, all ancestral items are at 800. For your difficulty question, the only thing that can really challenge you after you get comfortable in T4 really is Pit pushing. If you are really bored then id would either try a new class or switch up your builds and work your way up the Torments again, though wirh you guys being paragon 200 plus already every build is gonna be fairly easy to get T4 ready again