Coming into this late, so you might have made your decision, but re: XT vs SLX, my Rumblefish came with all SLX back in 2011, and I figured, no worries, I'll upgrade to XT as things go. Well, it's been a couple years, that bike's had all types of use, and I am now a massive fan of SLX. In fact, there are some ways that I personally prefer SLX to XT/XTR, having had the chance to ride both higher groups on other bikes. Now, obviously, that's not to say that if you went with XT you've done badly, I love the Shimano stuff. I'm just surprised _how_ good the new SLX is. I would say without reservation that new SLX is notably better than XTR from only a couple of years ago. Seriously.
Re: the Flows, those things are freakin' bomber. Depending on your weight, they're probably far more than you need. I once hit a 3" raised concrete lip at about 20mph hard enough to double-pinch flat a Kenda Small Block 8 (not the thinnest sidewall, either) and the rim showed _nothing_ after the fact. Just happened to catch it, you can just see the edge on the little bridge at the beginning of the video:
I've been running an Arch wheelset as well for a couple years, and even those have been bombproof, and the Arch EX should be even moreso. I'm 210-220lbs just for reference. Even the Crests are surprisingly strong, but if you're in my weight class, they might not be _quite_ enough. Although it's not cheap, I think a Stan's ZTR/Hope Pro wheelset is close to the perfect MTB wheelset. No experience with the Chiner carbon rim wheels, at least not yet.
