From the rough picture below, my *guess* is that Janka hardness of the Shin-Kaya to Agathis range is 480-1350. Kaya is reportedly softer than Shin-Kaya, so perhaps the goban-suitable range should go even softer for suitable woods. Agathis is listed qualitatively on Kiseido as "much harder than katsura", "advisable to use only glass stones" so this seems to be a decent upper range (and for the Janka hardness of Agathis, I'm not sure I've got the species correct).
I was unable to find (in a few minutes searching) the Janka hardness of kaya or katsura, but a few other popular goban materials are below. It would help if we could positively clarify the scientific names of the interesting woods. Many woods with similar common names have very different Janka hardness. I am no expert, just a simpleton with a finite amount of google-fu. I do not know the other qualities of these woods, i.e. crack-resistance or grain patterns or size availability.
Species List (guessed from mostly wikipedia, not positive these are the species for gobans)
Torreya nucifera - kaya (榧?) or Japanese nutmeg-yew.
Picea glauca - Shin-kaya is usually Alaskan, Tibetan or Siberian white spruce
Fagaceae spp. - (Beechwood) Beech (Fagus) is a genus of eleven accepted species of deciduous trees
katsura 桂, - Cercidiphyllum is a genus containing two species of plants, both commonly called Katsura. They are the sole members of the monotypic family Cercidiphyllaceae
Cercidiphyllum japonicum - katsura
Cercidiphyllum magnificum? (10m tall) - katsura?
Poaceae, subfamily Bambusoideae, tribe Bambuseae - bamboo
Agathis spp. (20 species) ("much harder than katsura", "advisable to use only glass stones")
Various Janka hardness (with references)
http://ejmas.com/tin/2009tin/tinart_goldstein_0904.htmlKauri, Agathis : 1350lb
http://cdp-praha.eu/content/3-janka-hardness-scaleKauri Ancient {Agathis australis} 660
Spruce White {Picea glauca} 480
Beech American {Fagus grandifolia} 1300
Beech European {Fagus slyvatica} 1300
Bamboo Natural {Bambusa bambos} 1375
Bonus woods (my selection)
Cedar Red Eastern {Juniperus virginiana} 900
Cedar Red Southern {Juniperus silicicola} 610
Poplar {Populus deltoids} 430
Cypress, Australian hard 1375
Cypress, Mexican 460
A few other references, including conversations in woodworking forums.
http://www.talkbass.com/forum/f8/agathis-wood-92273/"Agathis is in the pine family. It's most often used in making furniture."
http://www.fpl.fs.fed.us/documnts/fplrp/fpl_rp643.pdf"Estimating Janka Hardness from Specific Gravity for Tropical and Temperate Species"
Mentions katsura in the analysis, I couldn't see the Janka hardness from this paper. Have a look.
http://www.ibiblio.org/japanwood/phpBB2 ... a8e0d1bf85(Great list of Japanese woods here)
"Kiri, called Paulownia or Princess Tree, is commonly used for interior parts of tansu, though often enough the whole chest is made of kiri as well. It is very light, both in color and density, and very stable in service. Sugi is a common enough substitute for kiri for interior furniture panels, drawer sides, and so forth. Keyaki is a common choice for tansu carcase pieces as well, often lacquered. It has a vivid flat grain appearance. Hinoki use is confined mostly to household shrine furnishings and the like, and is too soft for regular use as a furniture piece. "