Go ahead and invest..
I made the mistake of buying an "off" brand of cold weather cycling tights a month ago. About half of a mile into my first ride I was regretting it. Although I literally just received the tights and tried them on, I was amazed over how incredibly comfortable they are. The chamois is amazing and the overall fit was perfect. I've read a lot of reviews on tights, shorts, jersey's, you name it. Castelli is a quality product. The sizing is European so check the measurements on the Castelli website.