These are the official recommended power requirements based on your graphics card:
500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)
This applies to the entire system not just your graphics card.
As you can see from the above you only need a 600-650W PSU if you plan to Crossfire in the future. If not then you can comfortably use a 500-550W PSU and save yourself some cash.
By 4 pin connector I'm assuming you mean the 4-pin CPU Power connector? Most of the newer, higher end PSUs come with a 4(+4)pin CPU Power connector which provides an extra 4 pins for motherboards that have an 8-pin CPU Power connector. The reason for the extra pins is largely due to the increasing trend of multi-core CPUs and hence the increased demand in power. The CPU power connector on most PSUs give you the option of using either 4 or 8 pins. The extra 4 pins usually clip on or off depending on your motherboard. If your board has 8 pins use the full 8 pins but if not then you should be fine to just use the first 4 pins of the connector from your PSU.
Recommended brands are Corsair, Seasonic and the newer Antec models.