Hi Kate...It's hard to say what things are worth without going item by item. More than 400 English potters alone produced the willow pattern, so there is a lot out there, and not all older pieces are marked. Some quick searches on ebay might be your best bet. Remember, the antique shop or a dealer will give you at least 50% less (probably higher) than what "they are worth" to allow for resell. And that will depend on how much they know about the value of willow in 2015. To judge by makers these days doesn't matter as much as what the item is. Pieces made in the U.S. (except for Buffalo Pottery), are probably worth the least and the most plentiful. New pieces are well...new. Not sure about Rising Phoenix, but there is a Double Phoenix pattern made in Japan. I think if this is something you have to sell quickly, I'd spend some time on ebay and do some searching first, if you can. What part of the country are you in?
Jeff