If you're able to pay for the fastest featherweight in the biz, a set of Crankbrothers Synthesis XCT 11 wheels should top the list of trail and XC considerations.
Given their precise build and lifetime replacement warranty, the Evil Loophole mountain bike wheels are a solid upgrade for any aggressive gravity rider.
If you've ever raced XC or marathon you likely have an internalized sense of what Red Zone means, and those are precisely the disciplines these MTB wheels were designed for.