I bought the Thor Attachment ( Welcome to ThorAttachments.com ) latch boxes and will build my own frame to fit my tractor. They look to be very well built!
I got the thor unit also. Just the boxes like you said - was around 450 if I remember correctly (this past summer). I cut the mounting brackets from my bucket and welded them to the boxes and painted. Here is a couple pictures and a video of it in action. http://youtu.be/vhjJTKPlMRk
I have not been gentle with it at all and it seems to be just fine - I don't even think about it any more - it is just another part of the tractor.