I haven't ordered anything form AquaCon yet, but I was fairly satisfied with my saltwaterfish.com purchases; the prices were pretty good, mostly everything was very healthy (except for a sixth extra [out of a pack of five] shaving brush plant they included that died about 2 weeks after it arrived, but I still have five healthy ones), though with the exception of the mandarin dragonet, they were all very small.
GARF, however, I trust implicitly. Leroy and Sally Jo are extremely knowledgable, and tremendously helpful if you have any questions or problems; they're a research institute staffed by people who are passionate about what they do who only sell a few items in order to supplement their research and in order to encourage people to use aquacultured items whenever possible.
Just make sure to call them if you want a freebie tossed in - they almost always offer whenever I call to order, though your chances are 50/50 for an online purchase - tell 'em Rupert and CJ, the guys who keep ordering tons of janitors from them, sent ya (not that it'll make any difference)
If your tank is new, I'd suggest ordering some Garf Grunge as well; they included some as my freebie on my first order of janitors, which will do your tank a lot more good than a coral or two, which is not likely to survive long in a tank less than a month old. If you give them some brief details on your tnak, they'll custom-build you a janitor pack, usually, to fit your needs. Don't expect any starfish or nudi's or anything... Just a lot of really healthy, reef-safe hermits and various snails; other assorted micro-organisms, stars, etc., will show up in the grunge or grunge plus.
One other note about grunge - if you have lots of pretty fine white sand, you may want to consider digging your sandbed up and placing the grunge on the bottom of your tank, as the grunge is basically a coarse rubble. I poured mine in at the bank of the tank behind my liverock, but my diamond goby has since redistributed it all around my tank to his liking, and digging my sandbed up would likely kill my tank at this point (plenum), so I'd suggest considering doing so now before it's too late. If you do, go ahead and get a couple pounds worth, and not just the 1lb. freebie. Your tank will definitely thank you for it. Avoid introducing any new stock for a week, and you'll already see the results of the grunge alone.
Or, you can follow the method listed here for