Thank you for the comments. I was beginning to wonder if I had done something wrong!!
I will have a think about boosting. I can at least try it out. The dip above 40 is pretty significant so I am not sure what improvement will be possible. There appears to be a lot more headroom on the Monolith so it may be worth a shot.
I wasn't aware that people were smoothing their response curves. That makes me feel a bit better!
I didn't have much filtering above 100Hz but there is some. Originally I had not planned to do anything above 100Hz but it was pretty bumpy so I thought I might try it out. I will reconsider that.
I have tried some phase adjustments already and I think I have got the best result I can expect!
My mains can easily handle a lower frequency crossover but my processor cannot so I don't really have any options there
.
Many thanks
David