And that brings up a previous point Beni made. The combatants can't just go anywhere. (Unless Beni wants to clear that up a bit more)
If Xizor knows who he's up against, I assure you right from the word "GO" he'll be burning lines trying to get away from Coruscant and his almost-defenseless palace. He does have a fleet and a personal ship. I think Kun will be forced to face him in a space battle. He certainly won't be unprepared for Kun's attack. And hyperspeed isn't a split second and you're there.
Also, I think Guri could kill Mandalore.... but not Ulic, obviously(?).
Mandalore was quite skilled in battle, but obviously Ulic will destroy Guri.
Edit: and the Empress Teta system is like right next to Coruscant. So they will get there awful fast.