Well, I'm not sure how much is set in stone about the Xorks. As I understand it, the Xorkaelians are insanely violent and xenophobic. They consider combat to be the first and only choice when contacting a new race. According to an excerpt from Captain's log #27, they had trouble with the Andros on their side of the galaxy and built up their technology to fight them. Upon learning the Alpha octant races had beaten them, they launched a war aggression, realizing they were powerful enough to be a threat.
I think the Xorks might be some sort of bizarre religious fanatics or a cult of some kind. I'm remembering SVC saying something about "at the center of their ships are the citadels, from which the single Xork controls the entire enslaved crew". Sounds pretty strange and creepy to me.
As for their ships, I believe they are supposed to be on par with X2 ships from the Alpha octant, but they have an unusual edge: their ships are incredibly modular. They take the concept to a degree the Alpha races can only dream of. They can literally create any type of ship they need in a few weeks using parts so easy to assemble and disassemble they're practically legos. They can make a frigate, a war cruiser, or a dreadnought out of the same parts and they can do it easily, without a large shipyard on hand. This gives them an incredible advantage, and makes them very capable of fighting far from home.
The Xorks sound a little too insane and paranoid to ally with anyone, also since they control five massive sectors of the galaxy known as "Xorkaelian Slave Sectors". I'm guessing that who they cannot enslave, they kill.
Anyway, I'm looking forward to the Xorks. They sound like they will be fun villains who we'll love to hate.