If spitting, hissing and clanging are your problems, it would be a much more economical solution to fix that problem rather than replace everything. There are ways to fix such things in both Steam or Hot Water Radiators. If these are radiators in an old early 1900's house, they have lasted a century and they were built to last another century. I have pretty silver decorative ones throughout my house. But I had no radiators in my two bathrooms and baseboard heat was added to both. One of them has already been replaced after only about 10 years, rusted, dented, yes. The other one is only 6 years old, somewhat sturdier and seems to be doing okay, but it certainly doesn't heat the room very well.