POWER SUPPLY NEEDS FOR VIDEO CARD IS MY POWER SUPPLY STRONG ENOUGH?

A few months ago I asked about putting a PCI express video card into a computer I had, and at that time was told by several people in this forum that the power supply in the computer was not powerful enough to put in any thing but the most very basic of video cards. I decided to not even bother, and gave that computer to my wife.
Now I’m considering buying a barebone system, and I want to make sure that the power supply in it would be adequate for a low to mid range card. keep in mind I am not a high end gamer ( I currently have an AGP Geforce FX 5200 in my current system). I want to be able to put in a better card than I currently have, but I’m thinking probably a $100 or less price range. here are the specs for the power supply as listed on the web site. is this adequate ??
# 550-watt power supply

4.5-inch fan

One (1) 14-inch 20/24 pin ATX power connector

One (1) 14-inch 12V ATX power connector

One (1) 14-inch SATA power connector

Five (5) 14-inch 4-pin large Molex power connectors

Two (2) 14-inch 4-pin small floppy power connector

Supports Intel Pentium 4 and AMD motherboards

Low noise and ripple

Short circuit and over-voltage protection

Thermal overload cut-off protection

Power Specifications:

115V, 230V switchable power supply

+3.3V @ 28A

+5V @ 40A

+12V @ 20A

-12V @ 08A

-5V @ 0.5A

+5 Vsb @ 2A