Congrats on taking your pond to the next level! You've gotten great advice above, and it sounds like you've done your homework too. Your thoughts on running at 8-10ft of a 15ft hole are good, there's been much discussion here on maintaining some sort of a thermocline as a refuge.
I run the same pump as you and will comment on that, it will easily perform at that depth. Since you haven't installed it yet, it's noteworthy to mention that it will easily run 3 of the Matalas also. The variables to keep in mind are, the length of your runs, and hose diameter. Bigger is better here, I recommend using 3/4" lines. Also, to have even flow at the various depths/distances, a valve station, where the lines branch somewhere near the waters edge is a good idea.
