Again, what Northwind said. Schwalbe tyres really are the “Snake Oil” of the mountain biking world… No better than anything else (and quite often worse), and very expensive, yet every fool seems to want them!
Right, those X-King’s are supposedly pretty good, as long as you get them in Black Chilli and a 2.4″ (they’re more like most 2.3’s, they’re from the old school conti sizing), but I’d only run one on the back, doesn’t look like it has enough bite for the front for me.
My default tyre combo right now that works an absolute treat for me, is a 2.2″ Black Chilli Rubber Queen (from the new school conti sizing, it’s more like most 2.4’s) up front, and a 2.25″ Maxxis Crossmark out back. This I find a perfect combo of grip, speed, light weight and comfort. Depending on where you ride though, if you ride slightly softer trails and don’t mind a bit less speed, either put another 2.2″ Rubber Queen out back, or just put another 2.25″ Advantage on the back.