I don't have any problems with the eye candy but I only use XP's default themes - I don't any of the aftermark stuff.
While you can get XP's memory usuage down quite a bit with a few settings tweaks it won't run using as little memory as 2K does as it's had it settings tweaked. 2k just runs faster on a less powerful box.
I'd strongly suggest not using any of the theming programs out there for Windows. They've caused more problems than I ever though worth while. If you want something that you can skin to your heart's content get Mandrake and use KDE for a desktop. There are more themes for KDE than a body could count.