So I think the first question we need to address before a true answer is given on set up components is what are you looking to run? Do you want to start out with a flat out 6S 550 class bird or do you want to jump straight to a 12S monster set up?
If 6S, common components are:
Scorpion 4025-1100kV motor with a Castle 120HV ESC or other high voltage high amp ESC
Battery packs that are 35C and up with 4400 mAh to around 5000 mAh capacity.
High voltage servos of your choice are your best bet; A very popular combo are Futaba BLS255 on cyclic and BLS256 on the tail. The 255's seem to have been recently discontinued so another option is the 272's or the JR8717HV or JR8917HV combos on cyclic. Other brands to look at are MKS, Outrage, and Hyperion to name a few.
Honestly, I am not sure that I need a 12S- I recently put a 40A YEP ESC and Wicked 4800kV motor in my 300X- Let me tell you, the little fellow drills holes in the sky and makes it rain. It makes my 450X feel like it needs more umph, and I end up cutting the throttle down with the transmitter.
So, as you can see, I am not sure that I need a rocket ship (I've only been flying since March)- I like the pop, but I am no professional. I am perfecting my inverted flight. I have the inverted nose in hover down for a whole battery pack, but I'm still trying to get the inverted tail in hover to last that long, and then of course, start flying upside down circles, and do the tick tock thing.
Is there any reason to get a Castle ESC? I can get the YEP 120 for a lot less and I already have a YEP programming card.
Synergy helicopters are produced in small numbers and I can assure you that no one in the business is more concerned with quality control than Matt Botos.
What about availability? I am perfectly capable of drilling my helicopter into the top of a tree at 70mph. I did this with my 450X a couple weeks ago because I was trying to fly too late in the evening and could not tell which way it was facing..haha..
I have a DX8 and experience with the BeastX. I also have a Spektrum reciever that came with my DX8 as I fully intended to get a bigger heli when I bought my first Nano..haha.. Is there any reason to change radios or flybarless systems?
FINALLY:
Thank you everyone for all the informative and thought out replies- this plays huge in my thought process here.