In the JD 455 equipment compatibility table it is the 450 tiller listed to go with it. So it seems John Deere intended for the tractor and tiller to work well together.
425 Has a PTO HP of 16If memory serves me right, your 455 has about 24 HP, the JD 1023 has 23 HP. I believe the soil your trying to till would be more of an issue and that can be handled by taking shallower passes. I would not worry about it.