Well... here are my cents, as I have been looking in to video cards, cpu, and mother board specs lately.
As far as processor power, the P4 2.4c, 2.6c and 2.8c will all out perform the AMD athlon and barton series up to the 3200+ model, BUT, you need an OS which supports Dual CPU's and have that option turned on for the Hyper Threading to work, as well as have a HT enabled Mother board. I don't know if wind98se support 2 cpu's but I am guessing no. As far as windwods goes you'll need win2k, NT, or XP for the HT feature as well as a mobo that supports HT (hyper threading.)
It has been reported that a standard 2.4c is the same exact architecture as the 3.0 P4 (but with a lower default clock speed of 2.4c), and that you can over clock it up to 3.0 safely because of this. BUT, it has been specualted that the reason why the 2.4's are being sold as such is due to die quality. I don't know much a bout die quality, but I do know that die quality dictates chip quality and chip quality dictates price.
I myself was looking at the 2.4c untill just recently. I may go with the 2.6c or 2.8c because I am not in to over clocking (though my board supports it quite well.)
As far as video cards, the ATI cards do not yet meet the standardization for visual quality that NVidia set up for the actual appearance of textures being rendered during a scene. I would have said go Radeon until I read and saw the difference on tomshardware.com just last week.
The Radeon does have a higher frame rate, but at a visual cost to textures rendered for details on explosions, lens effects, and similar effects.
The NVidia options will all have a lower frame rate that the Radeon comparables, BUT, they will be rendering more textures and details per detail level than the Radeon, due to above mentioned problems.
I have a personal kind of dislike for NVidia... but that is because they used the same tactics that ATI is now using for gaining control of the video card market, and closing the doors on 3Dfx (which I think was the greatest of it's time detail, Anti-Aliasing, and blending of a scene to get rid of the jagged feel.)
THOUGH, NVidia is now making texture rendering standards and suprisingly sticking to them... I would o with their cards, just because I am more interested in more detail, and not more FPS (hell, the average human eye can only see about 35 per second they say... seems kind of pointless to have all those extras, even if I can see them.)
So........ You will get lower FPS with the comparable Nvidia model, but Higher qualitty than with the ATI, which will in turn have higher FPS with lower image detail renders.
As far as video cards, it is your pick.
As far as CPU and mother board, it's your wallet, but Intel does have an edge these days.
I suggest yoou read the video card review and mother board review sections from
http://www.tomshardware.com before you make a final decision.
Peace!
(not that it matters, but I am going to run the pentium and a nvidia together. The mobo and ram are all I have purchased, and they were both LE at 428$ total! arG!)