BlueZoo has great quality livestock. I also have had great experience witih the LiveAquaria.com
, and SaltWaterFish
The problem is that these sites have reduced or free shipping with orders over $xx. Unless you are stocking a 500+ gallon tank and ahave a 125+ QT tank you would be adding too many fish at a time to meet the shiping guidelines. If you are adding inverts, corals, etc. at the same time then it works.
In most cases buying from a great local LFS
costs the same when shipping charges are included.