First off, STAY AWAY from the MX series. They're really just a bunch of GeForce 2s.
The TI series is all good (4200, 4400, 4600). They're based off the new chip, and they put up impressive numbers.
The 4600 is THE ONE. However, it's $400, so it's probably out of most people's range.
The 4400 is good, and it's $300.
In 8 weeks, they'll release the TI 4200. It's probably the best deal - it may retail for $199, making it the "TI 200" of the GeForce 4s. If it bechmarks well (and it most likely will), it will be the best buy.