http://www.newegg.com/Product/Produc...82E16814102407
That's an Radeon 9600 Pro for $80.
If you're really not looking to spend more than $150 that's what I'd recommend. You can get a 9800 Pro for $165, and if you're willing to spend that much I'd say go for it. It's a generation old tech, but still a very solid card.
If you do go with a Radeon, get one manufactured either by ATI or Sapphire.