I dont see your problem, all those components are compatible with eachother. Perhaps your asking what upgrade youd like to make? For Dota 2 thats fine.
I dont see your problem, all those components are compatible with eachother. Perhaps your asking what upgrade youd like to make? For Dota 2 thats fine.
If you are only playing Dota 2 then little benefit to upgrading.
However if you plan on playing more demanding games such as Battlefield, Call of Duty etc.. a cheap(ish) ~£60 upgrade would be an Athlon x4 860K, it offers the same performance as the A10 7850K at a much lower price.
If your budget allows I would suggest the i3 6100 as it offers a large performance increase, but this would require a motherboard change too and cost in the region of £150. It would be well balanced with your R9 280x and manage 1080p gaming for all current titles.