Instead of asking "where to find LR", you might ask "what KIND of live rock do I want", (Atlantic gulf, Fiji flat shelf, Tonga branch?) and what kind of life do you want on it (sponges, plant, purple coraline.?)
As you mentioned quality is very important, may I suggest to get the rock right from the diver or collector. One thing I've seen time and time again, is the more middle men and hands that are in the chain between the diver/collector and you the consumer, the quality suffers as it gets more and more picked over with all the good stuff going elsewhere. Way too many transhippers and middle men. Typically there are about 5-6 different transactions between wholesalers till the rock reaches your local pet store.
There are many sources such as Gulf View or Tampa Bay Saltwater that collect and harvest their own Atlantic aquacultured rock. Finding a direct source from the south pacific is a bit harder, but you can locate many marine life sources at http://www.aquafind.com
Live rock is probably one of the biggest expenses to setting up a reef, and when some places try and pass off dead bare limestone base rock as "premium" and charge $6-10 a pound for crap, it really pisses me off when I know what true killer live rock can look like right from the diver.
I know you want to buy rock online but... I saw some nice looking rock at the shark reef in Silverdale a couple weeks ago. They seem to always be getting nice shipments in. I would check them out at least, you wouldn't have to pay for any insane shipping either!