Dimensions of Exo nano are 8x8x12" high?
What size footprint are you thinking about for your light, and do you plan to have the light fixture sit directly on top of your terrarium, suspended, or maybe attached with an arm (something like the small pendants they use for planted aquariums)?
Seems many of the viv folks are very satisfied with the Spectral Designs that you mentioned above. As far as plug & play alternatives, I'm not going to be of any help.
I have a small 8x8x12" glass terrarium with a small DIY light sitting directly on top. It is powered with a single 3w Cree cxa1304 6500k chip (9v @ 300ma). Performs really well for low light orchids. An inexpensive build... fixture measures 6" long by 4" wide and sits directly on top. Basically, just a heat sink camouflaged with a wooden frame (makes it more eye appealing to me and eliminates light spill).