In reply to andyd1970:
My x-therm is very warm, at least as warm as my exped down matt 9. The x-therm is lighter. But as others said expensive and not as wide as you whish (to my knowledge) and beside that mine is noisy. But suppose … , if you go winter camping in Canada, buy a thick yellow foam matt at MEC and put it under your standard wide matt, works like a dream. Not that expensive. Or may be you can get a thick a Thermarest RidgeRest Solar to put your summer matt on top. Both will do the job well I think. But the shining of the aluminum coating of the RidgeRest Solar fades after about 3 weeks of use. (If you use it also outside the tent as a sit upon.)
The Z-rest is not as warm, I think, tried it once.