hi all

i was hoping a few of you might be able to help me out. at the moment im running 2x Sapphire Radeon HD 6950 Overclocked 2GB cards on 3 Monitors at 5040*1050 eyefinity and i think its time for abit of an update but i dont no what to get.
ATM money is a little tight so save up for a month is what i might have to do, witch is fine.
1st ill list a few games i would like to run in 3 screens with setting near to high as possible and getting a decent fps.

Star citizen
rainbow 6 siege
no man sky

im unsure what i would need to run 3 screen smoothly a few friends said that having a card with 4GB and over on memory shouldnt have a problem, are they right in that fact?
i have been looking around online and i think that nvidia might be out of my budget as much as i would love to get one they are tooooo expensive for me, well the 900 and 1000 series cards are anyway, i have never had one due to the pricing of there cards. but ATIs new RX 480 looks nice with its 8gb memory and for the price is kinda hard to pass up (250ish).

anyone got any idea im open to all and im in need of abit of help. if you need anymore info just ask
thanks alot in advance