Good question - and honestly, it depends on the level of filtered water you're looking for. Perhaps, for instance, you're only looking to remove chlorine and lead from your water; in which case, a carbon filter cartridge alone may do the trick - and it won't remove those beneficial minerals, saving you the job of remineralization. If, however, it's a must in your eyes that you remove the broadest range of contaminants from water, only an RO system may be able to achieve what you're looking for. In that case, you'll have to remineralize RO water should you still want to benefit from these minerals.