In reply to TobyA:
My experience FWIW is a fully rigid carbon 29er. When I was trying to work out what new bike I wanted to replace a 15 year old, scary to ride, XC race MTB I had a go on a mate's pimped Cube Reaction 29er. He had rigid forks, carbon bits and bobs on it, 1 x 10 drivetrain, XTR bits and it was just a smidge over 9kgs. With the grip of the 29er wheels and the lightweight it was utterly astonishing over medium rough ground. Like the difference between riding an 80's steel roadbike and a modern carbon equivalent. Night and day.
Carbon Reaction 29ers can be had for around a grand from various places if you get an older model, e.g.
http://www.paulscycles.co.uk/m1b0s155p5502/CUBE-REACTION-GTC-PRO-29-2014
I've not got a Whyte 29 CS 29er with On-one carbon forks and a dropper post and it rides like a an uber CX bike, with tubeless tyres and low pressures it flies over medium rough ground and goes down gnarly-ish stuff way quicker than a crosser. It isn't as fast on the road but it's not bad, and climbs exceptionally well. My set up is quite a bit more than a grand but the Cube will get yo most of the way there. I've ridden not so hard black trails like at Glentress on it, it was a bit rough but fine. I have a full susser for more gnarly stuff but it's amazing what the 29er soaks up even without suspension. And it is a 15 minute job to swap over the forks if I want to have the front suspension back on.
So for your grand you could get a couple of years old but new lightweight carbon 29er that will be suitable for lots of applications especially if you have rigid and suspension forks to swap in and out. NB. most front suspension forks are 15 thru axle and most carbon rigid forks are 9mm quick release, so I have a front wheel built with a Hope Pro evo hub that comes with different end caps meaning I can swap between thru axle and 9mm depending on what I need to do, but to be honest it's fine 99% of the time with the rigids on.