Win98SE has the majority of the updates needed for the operating system, and it is more stable than the original version. You COULD download nearly all of the bug fixes and install them, which would amount to about the same thing, but it might take you a while ... unless you have broadband.
If what you are looking at is an upgrade CD, just remember that you can't use it to install the OS on a freshly formatted partition.
I'm not exactly sure that you mean by Win98 "Plus", unless that is referring to the standard plus package, which is nothing but a bunch of desktop themes, cursors, .wav files, etc. That comes with the full version of Win98SE, in any case.
Win2K will cost you about 3 times more than the Win98SE upgrade. I think it is worth it, but if you are tight on cash, 98SE is the right move.
Toejam31
<font color=purple>If there was a reason for everything, having faith would be redundant.</font color=purple>