Stans Crest rim has an ERD of 541 according to the notubes web site.
For 12mm nipples I get as above suggests 261 Non drive side 260.2 drive side for the pro 2 eveo hub
32 x 260mm spokes should be fine for this.
For the Dt Swiss 370 hub i get 261.5 Non drive side and 261 for drive side calculated for 12mm nipples
you could go for 32 x 262 for this wheel build or 16 x 262 and 16 x 260
IF YOU WANT TO USE 14mm NIPPLES SUBTRACT 1mm FROM CALCULATED FIGURES AND RE-JIG SPOKE LENGTHS TO SUIT.
Have a look at rose bikes for your spokes, they sell them in packs of 20 so you would then have a few spares if one brakes down the line. Nipples from rose are purchased seperately but you should get all the spokes in black including nipples for less than £25 including P&P
[edit] by the looks of it of you go for 14mm nipples you should get away with 260mm spokes for both wheel builds [/edit]