[jfranci3]

At your budget, I'd be looking at TI frames (even used) and building the bike us yourself unless something really strikes your fancy. The tires will be handing all the ride quality, so looks and features over frame material though.

I'm not sure what ticks your boxes, but there's no need for CF on a bike like this for the most part. My old 2014 Trek AL CX bike with a fancy seatpost rides the same my new CF Checkpoint, even on the same road tires/wheels. You'll save a 1lb(maybe) and get slightly better cable routing, and that's it. The AL, Steel, TI,etc bikes might be better because of the smaller tube shapes. The metals are better than CF if you're riding in sand and rocks, as the battle wounds will look cool rather than expensive.


As for 650c compatibility, everything will take 650bs! The only question is how big are the rocks that you're going to be riding over. The 650b will wheel will be 20mm lower. As long as you're not 75mm+ BB Drop, you should be OK for most cranks/conditions.
If you ride a small bike, they may not clear the advertised tires. I know my Checkpoint is offered in 49cm, which doesn't clear the 48+MM tires my 58cm will (40mm? in smaller sizes).