If you create a monstrous site with a billion different CSS rules, then it might make sense to split some portions of the stylesheet's content. In almost all cases, it isn't necessary though.
I'd not split Eric Meyer's reset either, but place it at the top of your stylesheet. Be cautioned when using Eric Meyer's reset, however. He has added resets for almost all scenarios, like a framework, and many of the rules you find in there are not needed for a single project. And one more thing to be aware of is to make sure to read the comments within his stylesheet as it disables certain default browser styles that you can't just add back in via CSS and breaks some accessibility features.
Meyer's reset is good but it's overkill 99% of the time, so I'd advise that you create your own reset, resetting only the styles you will be using.