Sounds like an awesome tank! You could get quite a successful colony of azureus going in a tank like that.
Black jungle is no doubt an awesome resource for terrarium supplies. I have had personal experience with them on many occasions and have never once been let down. I must say that their selection and prices are not the best Ive found though. Check out cloud jungle epiphytes http://www.cloudjungle.com/
they have a gigantic catalog and pretty good pricing. I have no idea how their service is, but I will know in the next month because I will be ordering tons of plants and tree fern root for my 80 gallon viv.
I have no experience with either coco pannels or tree fern root but I am choosing tree fern root for my tank simply because thats what all the dutch boys use in their goregous tanks and I havent heard anything about coco pannels.
Black jungle is the only place Ive ever seen ghost wood.
My philosophy is to not mix species. Never ever put a tree frog or mantella in with a poison dart frog. They all require different vivarium conditions and could possibly trasmit dangerous toxins to each other. But if you did at most mix dart frogs, there is less chance of hybridizing if you dont mix the same Genus ,i.e., Dendrobates azureus
with Dendrobates tinctorius
but instead Dendrobates azureus
with Phyllobates vittatus
ect ect. It is less likely, yet still very possible, that frogs with different genus will mate. Keep in mind that if a male frog sees an unguarded clutch of eggs lying in the moss, he isnt always going to know what female laid them, and that wont slow his sperm down for a second.
Hope you have a blast setting up that tank and let me know of any other questions!