I am going to say the overpriced BBEdit.. but text wrangler is good too.. but really you just need a nice simple text editor and a lot of knowledge resources... really the editor tool should be ambiguous.
I tried stylemaster and cssedit and they seemed rather slow and boggy (having to update their context-sensitive stuff so often no doubt.) Now I just stick to textmate for everything. Column editing is absolutely smashing for html and css. Plus there's syntax bundles and code snippets galore. Someone even did a php function lookup, so I'm sure a cool css reference would be possible. Heck, someone might already have done it.
CSS is not all that hard to learn, and it is easier just to do it yourself. Get a good book like Elizabeth Castro's book, "HTML for the World Wide Web, Fifth Edition with XHTML and CSS: Visual Quickstart Guide." The title is almost as long as the book, but it is an easy read but technically complete.
My web site of over 700 pages has nothing but hand-coded CSS, and all formatting is through CSS. I have two main stylesheets, one for the screen and another for print media, plus ten others for specific pages that have special needs because of their content. So I'm speaking from a little experience--and I am completely self-taught.
Get a book and run your stylesheet through the W3C validator. That's the best solution I've found.
That's my suggestion. It's amazing how much control you have over specific elements, not to mention how much easier it is to troubleshoot, since you know how to read/understand the code that *you* put there.