My personal opinion 3 monitor current or near current cards:
For legacy engines simming (FSX, IL COD, Skyrim, rFactor2 etc) : GTX 680 or wait for GTX 685
For general gaming on modern engines (BF3, iRacing, Dirt3 etc): HD7970
One Other option you have is SLI your current card with either another 460 or I've heard it will SLI witn the 560Ti/448 like mine, but my personal experience is SLI and crossfire is hit or miss on whether particular games benefit from it or it causes problems.
Your mileage will vary that is just my own personal opninion.
email@example.com, Asus P8Z68-V Pro/Gen3, 16GB G.Skill@1600, Noctua D14, EVGA GTX 670 SC 4GB, X-Fi TitaniumHD, HAF932, Corsair TX850, Win7x64Pro, 3 x P2310H monitors, TrackIR4, Saitek X52Pro + Pro Rudders + Cessna Trim Wheel, Fanatec GT2 + G27 pedals + TH8RS shifter, Sennheiser HD580+ Modmic