Advice needed with hard ride
 

Hello,
I'm new, I bought by first Subaru (a 2005 blobeye WRX wagon with PPP), and now I need some advice. The ride in my car is very hard, to the point it’s making my youngest son feel ill on long or cross country journeys. I REALLY like the car so don't want to swap it.
I suspect it’s the 18” wheels (Prodrive PFF7's with Goodyear F1 tyres) and hard tyres as the suspension looks standard. Do you think it’s make any perceptible difference if I swapped to 17” with a sub 90 strength sidewall? The new tyres and wheels would cost approx. £800 so I’d like have some confidence that it will help before I spend that amount of money.
All (sensible) advice gratefully received.
Thanks Advice,
Stuart
PS. The car swap option would be for a 3.0 Legacy R spec B.