I honestly don't think they are making the 1523 for 2013. I didn't think they were making the 1526 either, as you can't even click on it in the Massey website. But they do have one on the lot at my local dealer. It does not come with a Mid PTO, but you can get it as an extra option. The 1526 IS CONSIDERABLY larger frame wise then the 1523 was. So I don't know if size is an issue for you, but the 1523 and 1526 are quite a bit different weight and stature wise. The 1529 is another jump again. Personally, I was not very impressed with the 1526. There are nicer tractors out there in the size. The 1600 series tractors are very nice. If you indeed want Massey, and they are not making the 1523, which I believe to be the case, there is a MAJOR jump from the GC series to the 1526.
I also noticed that all of the tractors on my dealers lot this year sport the OLD hood design. I have a brochure showing all of the tractors with the modern styling that the GC's currently have. But none of the other tractors on my dealers lot share this. I don't know what the deal is with the brochure that shows all of the tractors with the modern hoods.