lovely car, and in fantastic condition. Its a rare car, and becoming a classic sought after model - especially one in such good condition . Good luck with the sale.
I reckon the Volvo forums, and Pistonheads would be the best place to advertise a model which will be sought after by petrolheads. Most dealers i've come across don't know what the "R" model is, so i best most buyers wouldn't know what one was.
If you don't fancy selling it, hike the price by another couple thousand....then convince the wife you're REALLY trying to sell it...hopefully you'll get to keep it for longer...