are you gonna do a reef or just fish?
Either way, the live rock will be plenty of filteration for that tank. For the sand...were you planning on live sand? if so, i'd get regular dry sand instead...it will be live eventually.
On you tank, a skimmer might not be completely nessesary, but it would definately help. Even something like a bak pak skimmer would work good, tho i'd suggest a coralife superskimmer 65.
the hob filter wont really do anything like a skimmer would. Just dont put any media in the hob if you do get one. Instead, you'd be better off putting some live sand, rock rubble, and a ball of chaeto or something in there to make a mini fuge.