GeForce4 MX cards are trash, just forget they exist.
GeForce4 Ti4200's ran at 250/444 origionally... now they run 250/500, 250/512, or 260/550 depending on the card you get.
GeForce4 Ti4400's run at 275/550... no other speeds available to my knowledge.
GeForce4 Ti4600's run at 300/650.
The Ti4200's that run at 260/550 (Asus V8420S) can often be overclocked to at least 300/650. I have the V8420S and it's running at 325/650 right now.