There are also many, many, *many* large and/or heated discussions on this in the Video forum.
Basically, for $150, the 9600Pro is the best you can get.
For $200, the GeForce FX5900 Non-Ultra is the best card available. Skip the 9600XT and 5700Ultra -- they perform only marginally better than the 9600Pro, and they cost a lot more (although the 9600XT does come with a coupon for HL2).
For $250 (or possibly less), you can get a RADEON 9700Pro or 9800Non-Pro (which perform almost identically). It performs similarly to the 5900NU, although it is much better at running with AA/AF enabled, and it's much faster at DX9 (although how much of an impact that will have on new games is debatable).
For $300 and up, the 9800Pro is the way to go. The 5900Ultra is also a possibility, but its weaker AA and DX9 make it, IMHO, likely to need replacement sooner rather than later. The 9800XT and 5950Ultra are not fast enough to justify another $100.