No, I don't think I've ever heard of Dorrance before. I have no experience with them. I am getting my book published, it got set back a bit, but I looked up a few things before I started looking around so I can help a little. I can help you with distinguishing commercial and non commercial publishers. Commercial publishers are the publishers that can give you national publicity. It is basically the major means for advertising. They produce and distribute your book in large quantities into the industry and they normally have better editing so that your book is better edited. It is a author's dreams to be accepted by publishers of this nature because the business is better and you are naturally recognized for being with them all around the world. You can go to this website to see a list of the major ones. http://lib.colostate.edu/howto/publr-com.html
They have people coming to them everyday basically, they want you to have a agent so get one before even looking in their directions. Here's a address with a little more information about commercial publishers. http://www.btsf.org/ws2leefl.htm
Non commercial publishers are just the opposite. They give you publicity, yes, but it's not as much as a commercial publisher. Non commercial publishers typically give publicity through their website and bookstores. They do small press. There are less quantities of your book to be distributed. For a small, non-commercial publisher operating within a discipline, success need not be measured in profits, but in the range, quality and number of books published; the need to avoid losses is not the same as a requirement to make profits. I highly recommend this for first time authors so they can see how many people buy their book and are interested before they enter mainstream with commercial publishers. I didn't go that route though. I went to an independent publisher.