Last year's Solly Impact 10 is a noodle compared to your XWave 10. The Impact 10 Pro is stiffer, but good luck finding one. I couldn't find a pair last year mid season. They stopped production for the new models this year.
This year's Impact 10 CS is a 120 flex, so slightly stiffer than your old XW10's.
I'm in the same boat as you, need to replace my XW10's. I just tried the Impact 9 (110 flex) on and it is the same flex as my XW10's (also 110).
I have Impact 10CS's on order.
If, at your size, you want even stiffer, the Solly Ghost is a 130 flex, but I'd bet you'll be fine in the new Impact 10 CS.
What size? There is a pair of 28.0 X Wave 10's sitting at the HV ski shop. They are a few seasons old and leftover, I'm sure the price is real good.