Shame on you
This army will steamroll on everything...maybe you will find hard to win objecitve games VS fast and MSU armies, but thats it.
Also, hope never to face any eldar D weapons spam...
6 knights are as hard as it can be, tough honestly i'd drop one castigator and take some sort of ally (i know your "limitation", but you are already taking 6 knights...what's to limit anymore??): i am thinking about some scouting skitarii grunts or Raven guard marines or even marine bikers. Maybe an inquisitor with servo skulls and some retinue on chimeras??