Go to www.pricewatch.com and click on video cards.
There are a few listed for under $150, but they are Powercolor or Gigacube brand, which have fairly poor quality/customer service rating. Right at $150 there are a few...
newegg.com has a Transcend Brand (don't know anything about that one)
allstarshop.com (and newegg) has a Sapphire Atlantis brand one probably your best bet for $150
gameVE.com has a Connect3D one for $150, I think I've heard that they are good too.