We need more information about the rest of your system, including power supply brand/model, your monitor's native resolution and at least a rough idea of how much you are willing to spend.
Motherboard-ASUS P6X58D Premium LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
Monitor HP w2207 1680x1050
CPU- Intel Core i7-920 Bloomfield 2.66GHz LGA 1366 130W Quad-Core Processor BX80601920
PSU-Antec TruePower New TP-750 Blue 750W Continuous Power ATX12V V2.3 / EPS12V V2.91 SLI Certified CrossFire Ready 80 PLUS BRONZE
Cooler-ZALMAN CNPS9900ALED 120mm 2 Ball Low-noise Blue LED CPU Cooler