I'm planning a shrimp only cube, probably some CSR or bee shrimp if I can get them, but if not then cherry shrimp.
The PKF cube has an 11w light, which I think will be about the minimum you'd want to put over 5.5Gal.
I'm planning on christmas or weeping moss I may also have some U. graminifolia & P. helferi from my other tank if I need it, but I'm not sure the lighting would be good enough. I'll probably include DIY CO2 through a small glass/ceramic diffuser.
I've got one of the arcadia pod's already, but thats also 11w, so not really any better.
What I'll find interesting will be seeing the different scapes/uses that people come up with when all starting with the same basic equipment.