I've used Dunlop Trailmax (not a common choice on Xts) in the past for the type of riding you're suggesting...

http://www.dunlop.eu/dunlop_euen/mc/...ight=-1&rim=-1

At the moment I'm using the very much more road biased Trialmax TR91 as most of my riding will be on road this year, but these have proved fine on dry forest trails.

http://www.dunlop.eu/dunlop_euen/mc/...ight=-1&rim=-1

Both are good on wet tarmac and the TR91 are very grippy and give good feedback in the dry, the best tire I've tried for road use on bikes with a 21" front. Can't cooment on Sirac, but either Trialmax I have found better than Metzeler Tourance (neither is directly comparable to the TKC).

Hope this helps, but everyone's opinions/experiences on tyres will be very different as I'm sure you will find out...