My hardcopy CDs are, in most cases, copies themselves that I burned from public libraries, friends CDs, etc.
You do realize that this is a blatant copyright infringement? Not sure why you'd want to share that information publicly.
As far as whether to re-rip; It depends what resolution you ripped them at in the first place, and how discriminating you are about the differences in formats. You do not want rez-up a file, so if you ripped them at low-rez and you want high-rez then re-rip the files from the originals. If you want quality audio you should choose a lossless format such as Apple Lossless right from the start. If the files were ripped in low-rez you will gain no additional quality by converting them to a higher rez format IMHO and you may even introduce some distortions. I don't know the Nero Burn sofware, but if the CD's are indeed direct copies of the original CD's then you can re-rip from the copies. If Nero Burn compresses the files, then you will have to rip from the originals to get the best quality. I don't think EAC is compatible with Mac - at least, last time I checked there was no Mac version of that software (PC only). I'm not sure if EAC files are cross platform(?).