World Wide Coral = Awesome
Coralmorphology is good too. Depends on what you want really. If you are looking for specific something or other it never hurts to post a WTB in the classifieds.

Lots and Lots and Lots of places is the answer to your question. Poke around, if you find a place that has something you like ask around and see what others have to say about them. I wouldn't limit yourself to just a few people.
You want WYSIWYG if at all possible. You want to look at what lighting the photo's were taken in. If a company doesn't post that info, it may be a good seller to walk away from. Most reputable sellers want you to have an idea about ACTUAL color/size because they want you to fork over your reefing addiction dollars to them

Do they have an arrive alive? If they do is for 2 hours after it gets to your house or a few days? What are the return/DOA policies...
The key is to not impulse buy on the intertubes, find something you like ask around, look other places THEN make a decision.