You could probably stay fairly close to where you are, with a shorter stem.
Sounds about right to me… All my DH bikes have been within 0.5" in length (though each of them a tiny bit shorter) than my XC bikes. I stick to 23-23.5" TT for an XC bike, and anywhere between 22.5-23" is where all my DH bikes have been (that's effective TT length BTW).
As you've got a Medium Soul Barney, would suggest the Small BFe with a long seatpost for sure (and a 50mm stem). It's only 0.5" shorter in the TT, but its got loads more standover clearance. The Medium would be no different to your Soul, just a bit beefier.
FWIW Robbie Rickman (Cotic sponsored rider) is 6ft3 and rides the small BFe, and he's a pretty bloody good rider! At last year's Megavalanche, he was just behind me on the grid for the qualifier. Start gun goes, he BLITZED past me (and just about everone else)… Needless to say, he did pretty well overall!