Upgrading CPU + GPU

[crapbandit]

I've been looking into getting a new card for 1440p gaming.
I've been waiting on the new amd line to come out for ages, but the stock coolers are causing me to doubt it's performance compared with the cooler 780s out there. So I think I'm gonna either get a zotac 780 @~£350 or the inno3d @400 ooooooooor the r290. If you could pitch in what you think i'd appreciate that

I currently have a Phenom II OC @3.8Ghz but I am certain will heavily bottleneck the 780. I'm using a ASUS M4N68T PRO mobo which has an AM3 socket.
How much performance dip could i expect from maxing everything out? Is it worth me buying a z87 board with 4670k as i get the new card? Or should i just get the card and see what it's like?

Any help or advice would be greatly appreciated. Thanks for your time.

 

[crapbandit]

No exact budget tbh. I have the money to get what I want and will pay for the new cpu and mobo if it cripples my performance. I am sorta dying to play some bf4 though.
Is there really much chance of the 780 going for much lower than £350 in the coming month?