The cpu's are so close together it will be a wash.
No bang for the buck.
My son has this motherboard: GA-F2A55M-HD2
http://www.gigabyte.com/products/product-page.aspx?pid=4374#ov
With a AMD APU A8 6600K Quad Core Processor
He wants to upgrade it to a: AMD A10-6790K Quad Core
http://www.ebay.co.uk/itm/AMD-A10-6790K-Quad-Core-4GHz-FM2-4MB-Cache-100W-TDP-CPU-Processor-/181738678596?hash=item2a50782944
He's got a EVGA Nvidia GeForce GTX 970 FTW ACX 2.0 Graphics Card with a 850w power supply. So apart from the CPU he's happy with his PC. So my questions is:
Do you reckon his choice of CPU upgrade will make much difference (ideally, I think he wants Arma3 to work better) or would you recommend something different, or general advice would be good all the same
His budget is £150
I hope this post has all the information you need to help. I'll gladly answer further questions if I've missed anything or you're unsure of something..
Cheers
Lee

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic