Here is an old thread that has some Volvo rotor discussion. https://www.ferrarichat.com/forum/threads/308-rotors.294861/
If cost is an issue, Superformance in the UK offer great value brake discs ( https://www.superformance.co.uk/308/brakes.html ) : Front: £159.85 each Rear: £168.00 each. From Ferrari or Eurospares, the front discs are @ £300 each, and the rears are @ £220~£320 each, depending on supplier. Brakes and tyres are two things I wouldn't want to cut corners on - They're pretty important when it comes to your safety.
Please keep in mind that if you order from overseas, my particular circumstance it was Superformance, that if there's an issue with the parts you are responsible for shipping the defective parts back overseas. My experience was with bake hoses. Obviously the wrong parts, sent photos to Superf..., their response was they dont pay for return shipping but if I got them the parts they'd replaces them. That was not cost effective, I got the correct parts from, I believe Rutlands. Apologies for running on. Cheers Toom
Surprising story about Superformance since every time I've had an issue they didn't even have me send the old parts back, they just made it right. Only one issue with Ricambi that I can remember and same with them. Maybe I'm just not buying expensive enough stuff!