Restocking a 270 will require a lot of livestock. With that kind of volume, I'd just do liveaquaria all the way. Great quality, huge selection, and probably the best guarantee you get in this business.
The best store around here is probably Elmer's. I've had mixed experience with them, they are not perfect but one of the better ones. I did get fish with ich from them every once in a while though. Also, if you are looking for specific species, it could be a hit or miss.