... Yes, of course they are 5V. That is the voltage spec for USB devices...
What matter is how much current PER-PORT the hub will provide. You want to have at least 2A (2000ma) per-port to run a 2PAC at nice speeds. As a general search, look for 'Charging hubs' made to power tablets and such.

Um there is a thread not to far away specifically about powered hubs and 2PAC's...

edit: Ok, so the thread was 3 pages in so   here is 2PAC powerd hub thread.