Upgrade Advice

Hi guys, looking for some help with my next upgrade as im kinda torn what to buy. i have around £3-400 (prices are roughly the same in USD) to upgrade my rig.

 

I mostly use my PC for gaming,atm im mostly playing BF4, dota 2 and a couple of other games here and there

 

My current machine

M5A97 EVO R1 

Windows 7 (64 bit) 

AMD 4170 Quad Core

AMD HD 7870 

Corsair Dominator 8GB 1600MHZ

Samsung 1&2TB Harddrive

Samsungs SSD 840 PRO 120GB 

Bequiet Purepower l8 530W 

 Thanks for your help

 

Stretch

 

I'd up the PSU to a higher wattage model, and grab either another 7870 and crossfire those suckers or a 290 with an aftermarket cooler.  The only other thing I might upgrade is the cpu, but there's really no need.

Would my CPU not bottle neck a 290? And should i go 290 or a 280x with looking at crossfire in the future?