Why joubini? For many years O. mercatoris has been call O. joubini but O. mercatoris is a large egg, relatively common octopus (though we have not seen many in the last few years) where O. joubini lays small eggs, is likely slightly larger and rarely available. Both are nocturnal dwarfs and quite reclusive (anecdotal observations suggest that O. joubini may be more active). A 65 gallon tank would be overly large for a single specimen of either.
Your 65 would be suitable for a medium sized animal (O. hummelincki, A. aculeatus, O. briareus) that will be more active, live to be somewhat older and seen more often.
Sourcing any octopus is a challenge. Some LFSs will order them for you and occasionally you will see them available on-line. Ordered animals are most often imported and frequently in the Abdopus group (often aculeatus) or a nocturnal we believe to be Callistoctopus aspilosomatis.
Here is a short list of links I recommend to all new octopus keepers. The Box of Chocolates thread gives a bit more detail on what to expect when you are octopus shopping.
Best guess without having a clue as to where it is from and general "look" as well as what has been acquired in the last few months would be O. vulgaris. But, as I mentioned on FB, a single picture can be deceiving.
A Caribbean common would not be "brown" as the Common Caribbean Octopus (CCO) is the common name for O. briareus and is rarely "brown" in appearance. The Common Octopus, is the common name for O. vulgaris (and is primarily brown). Often the name "common brown octopus" is also given to anything coming from Indonesia/the Philippines -- frequently something in the Abdopus complex.
If the chierchiae is correctly identified (area of capture -- South America/Panama and photos a must), it is very rare to find in the trade but a great large egg dwarf. However zebra is more often applied to Wunderpus photogenicus (usually imported from the Philippines). Wunderpus has not done well in captivity, the state of its wild population is unknown and is a lot of money for a normally very short captivity period. See the exotics forum for more info.
I know your looking for an octo and your ready. Take your time. Remember they have a very short life span and you have no idea how old they may be when you get them. For your first octo I would not go with an exotic. Lets say you got the exotic and it lived for 1 month. That might push you away from trying again.
Its very hard to tell a species from a single pic as they change colors and features.
Truly a box of chocolates pick . My guess is it will be an Indonesian import in the abdopus family but, assuming this is from Live Aquaria (it is OK to mention your supplier and I list them in our octopus list if given), it could be a couple of others from the same area.