EDIT...sorry, I posted this at same time as you.
Aquatraders best prices but awful service...products are about average to below...I'm using a 48" PC fixture that I love from them, BUT I've gotten other things not so good, and they showed something in stock that wasn't and they didn't respond to any emails. I finally just got a refund (though no contact) about 3 months later...but at least they refunded.
CustomAquatic is my favorite place and they work with you and talk with you.
Live things? All depends on what you are getting. I like saltwaterfish.com and marinedepotlive.com. The online places seem to have healthy critters for me so far, but you better be OK without seeing your "product" before purchasing (example: you order a small fish and it comes to you smaller than you knew they were even born at, lol).
Like the art lady said...whatcha looking for? That makes a difference.