Make shure you get a mobo that supports the faster 266MHz bus (or better). I used to have an older Athlon with 133MHz bus, but my mobo also supported running at 266MHz bus speed. Then I bought a newer Athlon with just 66% more GHz, and with a 266MHz bus. The difference was shocking. Like switching from a Wolkswagen beetle to a porsche.
And speaking of Parhelia. What got me hooked was the general IMAGE QUALITY. I clearly see the difference between f.ex. grey 127 and grey 128 in a greyscale gradient. Or any colored gradient too for that matter. 24-bit being beyond human vision is just qualified bullshit. More like beyond crappy hardware.
Don't buy a GF4 MX-200 (or whatever number comes after "MX") it's degraded crap. Any other GF4 will due.