Well i would recommend myself that lens too I have got the APO rodagon 50 mm and can say that these lenses are beyond incredibly good. So is the normal rodagon 80 mm that i have got.
But do i need that quality? Well if i make an enlargement of 20x25 from a 24x36 mm negative i am making a 10x enlargement. If i make a 30x30 from a 6x6 negative i only make an 5x enlargement. In the last case i could do with a lesser quality lens. In the past when i bought two enlargement lenses fron rodenstock the infosheet from rodenstock gave a list wich lens to use for wich enlargement. If you only make a 3x enlargement the stated that you could do with a rodenstock trinar.
But i have to agree that if i ran into an rodenstock APO rodagon 150 for a nice price i would buy that.
Unfortunately on ebay a lot of these lenses are sold from the US but the sellers do not want to send it to the netherlands most of the time.
But for the Ysaron, i do not know what to compare it to. Bur since i wil not be making big enlargements (say 4x at the most) i wil not be needing a rodagon quality is suppose.