Iron, I don't really know my stuff in this area but I'd stick with 8x.
Here's why: I find myself wanting 6x sometimes, and I find myself wanting 10x sometimes. This tells me I found the happy medium (For what I use.)
Kinda like picking a caliber of gun or draw-weight to buy. "Find a happy medium." I'm young, but I'm staring to learn that lesson...and it's treating me well so far.
Unless you're obscenely rich, then just buy one of everything.
I mean TWO of everything, I'll take the extra off your hands! :D