You have to decide whether to take an offer or push for a more suitable publisher. Don't let advance money get in the way of that decision. You want a publisher who knows how to publish your book. And when you find them, you have to push them to do it right. Left to their own devices, they'll put an OK jacket on it, print and bind it, and try to get some copies out.
Publishing is a partnership.
You know who it's written for and what will make them buy it. Do not assume your publisher knows more than you about this. The chances are slim that they do. If you want your book to sell, be prepared to do whatever it takes. Otherwise, you'll just be another title in Books in Print .