Attilio If you haven’t decided on something yet, I can recommend the Northwave Celsius XC Arctic GTX (or the previous model, Celsius Arctic 2 GTX) insulated cycling boots, particularly in combo with a pair of electric socks. That’s a roughly $300 setup, but it works better than anything both in terms of warmth and ease-of-use.
The Northwave Celsius are roomier than a standard road to accommodate a thicker sock, and roomier than the Mavic Ksyrium winter road shoes I also have and which I use, because the only fit a standard, thin cycling sock, for the range mid-30°F to 50°. The Northwaves with electro socks easily handle down to 0°F depending on sock heat setting.
I’ve been very happy with these options, and they really have economized my selection and dressing routine compared to old method of various sock weights, chemical toe warmers and overshoes.