Whenever you're looking at a graphics card, check out TomsHardware. They do monthly roundups for SSDs, gaming CPUs, and graphics cards. Here's the
June 2012 Best GPU for the money article. Keep in mind that this doesn't include various sales, so it's just a general guide.
At the $100 price point, you'll play the games mentioned at 1080p with maxed out settings. That'll likely be a Radeon HD 7750 or Radeon HD 6770/5770, or perhaps a GeForce GT 440 GDDR5 version. At the $150 level, you're looking at a Radeon HD 6850 or perhaps a GeForce GTX 560 SE. At the $150 price point, you'll be able to play most games at 1080p with good settings if not nearly maxed out, at least with games that are currently released.