I've got a C30, only a D2 but put B4s on it and v impressed with the handling so thought maybe it deserves a rear ARB.
I'm a fan of the Whiteline ones. I emailed their tech and he confirmed the Focus ST ones will fit our types of Volvo. BUT, they have vertical tabs and unfortunately mine has horizontal tabs.
So if you have the vertical tabs, looks like two Whitelines will fit. Both are two way adjustable. Both cost £167.50
22mm BMR78Z
http://www.whiteline.com.au/product_...BMR78Z&sq=5363
24mm BMR78XZ
http://www.whiteline.com.au/product_...MR78XZ&sq=5364
Hardrace do a 2 way adjustable 22mm which is cheap at £105.99 but it is a hollow bar, not solid steel so I'm not sure how much stiffer it would actually be - torsional stiffness??
There is also the Elevate. It is 3 way adjustable 24.5mm. Expensive. I believe Kalmar Union do these.
I've got a Whiteline chart that tells you the stiffness increase you get going from one diameter to a bigger one. Which you might find useful.