IMO always get the best single card your budget allows for. This avoids the headaches of SLI/XFire, but gives you the option to add another card in the future if you find you need it or get a great deal. I would consider SLI/Xfire as an upgrade path down the road and not a plan to start with.
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Desktop: Arc Midi R2, Z77-D3H, 3570K 1.09v/4.1ghz with Zalman Optima Cooler, Corsair Vengeance 2x4gb@1866mhz, XFX R9 280X DD, Bitfenix Fury 750w, WD Black 1TB, Intel 530 120GB
Away from home light Gamer: Acer Aspire 15.6", A8-3500m undervolt and OC to 2Ghz, 2x4gb Corsair Vengeance, Crucial M500 240gb |