Upgrading Graphics card

I have a Pentinum 4 HP home edition computer with a geforce 5500FX graphics card. I wanted to upgrade my card to a Visiontek Radeon X1550 Video Card, but is the Radeon better then the Geforce, and how much faster will it run. I heard of people geting into the 100s Frame rates for games like battlefield 2, and WoW.And if anyone else knows of a better PCI(not PCI-e,because my slots are only PCI) graphics card that better then the Visiontek Radeon X1550 Video Card, and thats lower then $160? If you need any more info please ask.

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