What power supply should i get?

This computer is prebuilt but i will be upgrading the graphics card. Its a Lenovo M90P i5-650

Here are my specs:

Intel Core i5 650 3.2Ghz

500GB SATA

3GB Ram DDR3 (expandable to 16GB)

XFX Radeon HD 6870



I will be using 3 monitors for this computer.What power supply should i get?
it should be just fine with the stock power supply
The recommended power for the HD6870 is :



500 Watt or greater power supply with two 75W 6-pin PCI Express庐 power connectors recommended



http://www.amd.com/us/products/desktop/g鈥?/a>



Thus for a single HD6870 GPU, a 600w branded PSU would be ideal (extra power for future upgrades and extra breathing space for your PSU).What power supply should i get?
Corsair Power Supply units are really good.
First of all, monitors do not draw power from your PSU, they have their own power supply.



Your power supply (PSU) is the engine that drives everything that's inside your computer. Never cheap out on a PSU. Get a quality brand name PSU (Enermax, Cooler Master, Antech, OCZ, Corsair), a modular one would be best.



For your system power needs, use this power calculator:

http://www.thermaltake.outervision.com/



Fill in all that apply, select capacitor aging 50% and hit calculate. Just to be safe for future upgrades and wear and tear, add another 20% to the resulting power and get a PSU at least that big.What power supply should i get?
I suggest a SeaSonic brand power supply. Corsair sold rebranded SeaSonics.

XFX, a well known graphics card manufacturer, also sells rebranded SeaSonic power supplies.

Here are two you should check out:

http://www.newegg.com/Product/Product.as鈥?/a>

SeaSonic 620 Watt Modular power supply



http://www.newegg.com/Product/Product.as鈥?/a>

XFX 550W non-modular



Both of those should fit your needs.