Power system consideration question

[Bobmic]

I was looking at Seagull Pilatus PC-9 1.20 and before going forward I wanted to consider the powerplant that I will be using for it.
The plane is 10-12lb and was considering something around 160-200W/lb.
Since it is not a tail dagger and I am not sure about the ground clearance I will keep the diameter of the blade to >=16inch as per spec.
Now there are two options and this is where I need advice:
1. Go with a 6s setup something like the Rimfire 1.2 462Kv and 16x10 x2 prop
Based on ecalc I will get 7700gram static thrust, 88Amp, 172W/lb and 62deg on the motor

2. Go with an 8s setup using something like SK5065 320Kv and 16x10 x3 prop (since I am not sure about ground clearance..)
With this setup and the increased weight I will get 8480gram static thrust, 73Amp, 178W/lb and 68deg on the motor.
This is somewhat of a sports plane nothing super fast nor 3D but it will be nice if it will have a nice speed - that's the reason for the 10" pitch.
I know that 3 blade props are usually less efficient but have no clue by how much etc. with the 8S setup I can gain about 15% flight time due to decreased current while keeping the same power to weight ratio.
On paper an 8S setup is better but is there anything else I am missing?
I would prefer to keep the setup with 6S as it is easier to manage the batteries and the only concern with 6S is the higher current and the fact that have the HXT 4mm connectors on all my batteries on HK's website they note that these are rated to 93Amp but I wouldn't know.
-I have better connectors including 5, 6mm bullets and the XT90s which I could use but would prefer to keep the same connectors on all butteries if possible.

...So any suggestions or preferences?
-I don't have much experience with HK motors (definitely not with the larger ones) as currently I am only using Eflite and Rimfire ...do these worth the x3 price tag?


http://www.rcuniverse.com/magazine/article_display.cfm?article_id=1402

just to throw another wrench I am considering this PC-9 or the H-9 Twin Otter which I know is a completely different plane but it definitely looks nice

...Unfortunately the 3DHS Bigfoot will have to wait as it's too expensive and seems to have many issues

Thank you
Bobby