As far as I know, nobody has worked out how to use carbon nano tubes to make armor. I'm under the impression they are working on replacing the adjuncts used in ceramic plate manufacture with the carbon fiber. Total carbon fiber armor is a ways off, but when it's real it'll be the shit for sure. Not that they can't use it for some stuff now --I have a carbon fiber 3A helmet, the Crye Airframe. It's hard and light. I'm not aware of any true lvl.4 carbon fiber plates. I'm aware of plastic rifle plates, polyethylene? They work against some lvl.4 threats, but not others. Hence, they don't have NIJ ratings.
If you want good armor, if you need it, Paraclete/MSA makes some of the best 3A, and you can get decent rifle plates from a major manufacturer from Bulletproofme.com. They'll be your typical ceramic plates, work great for the price. SAPI cut stand alone plates are best. They'll be rated.
If you just want shit to hang in the closet and hope you never need it, the OTV and IOTV can be had online cheap and with all the extras, and you can throw some AR500 plates in there if you don't plan on ever needing it (a just-in-case sort of thing).