I did some testing and sample prints for Glazers Camera here in Seattle, both color Ultrachrome and Piezography. The papers were Rag Photographique 310, Rag Photographique Duo 220, Montval Aquarelle 310, and BFK Rives 310. They all performed well, nearly as well as the Hahnemuhle line technically, and I'd say visually, virtually as well.
All of the surfaces were attractive, and the Rag Photographique 310 looks like a good option for HPR lovers. I'm looking forward to trying the other offerings. I also tested Platine Fibre Rag, which performed very well, and in the SilverRag types of papers, but thought it had a hair more gloss differential with UCK3pk than some other papers in the same catagory.
Tyler
http://www.custom-digital.com/