Based on the OP, I'm assuming this is primarily for XC use, and weight is a concern. If that's right, then something carbon that is easy to tension is probably the way I'd go - Pivot LES and Niner Air9 RDO (they don't offer the One9 anymore) are great choices. I'm actually planning on picking up the Niner this year because I love Niner's geometry. You mentioned slamming the front to get a low-front end - most of Niner's line has that kind of racey low front end already. I wanted something light and snappy to go with my Sir9 but I didn't want to lose that Niner feel, so the RDO is an obvious choice for me. BTW, Niner is also selling out this run of Sir9's and ending that line as well, so if you want a great, comfortable and raceable SS for endurance events, consider picking up that frame before they're all gone. The Sir9 is a great option for really long rides and races - never going to be as light as a carbon frame, but it's no clunker either and it takes a beating and keeps on rolling. And there is less concern of having to live with that creaking sound in the BB housing if you accidentally overtighten the EBB and squeeze the carbon housing. I don't think Pivot uses an EBB (they use a rear dropout that ... ummm ... pivots) so that carbon-specific issue wouldn't be a concern for those.
