Sounds like you are off to a good start!
ARP barrels are probably one of, if not THE best barrels in this caliber.
Mine love 120gr SSTs but the piggies in the area don't like them a bit!
I have taken over 200 pigs with them over the last 3 years, mostly at night.
My Nephew has taken a couple of nice whitetails with them too.
My son, who is much steadier than my 60+ years has shot a 5/8" 5 shot group at 100 yards with them.
As for powder, AA2200 is the king of velocity and pretty darned accurate too.
I found RL10x to have a slight edge in accuracy but is down just a little to AA2200 in velocity.
AA2200 is just slightly "dirtier" when shot and leaves a soot on my NIB BCG but wipes off easily.
As for brass, I am mostly using Remington LRP brass because that's what I could get at the time a few years ago.
SSA brass seems to be the bomb and will stand up to a little more pressure but I've had trouble finding it for a reasonable price - well, finding ANYTHING firearm related at a reasonable price has been tough but it's getting better.
Keep an eye on the primer pockets on the Hornady brass if you load at the upper end of charge weight.
The S&B brass I have used seems to be very soft and has trouble holding primers after only 1 or 2 reloads.
Good luck Sir and if you have questions, I will try to help but the best source for all things 6.8 is www.68forums.com.
Harrison from ARP hangs out over there and the knowledge base is the best there is for that caliber.
And welcome to the 6.8 family!