My first direct rig was a Studio Preamp with an Alesis Quadraverb GT in the loop; speaker cab simulator on in the Quadraverb and used speaker emulated outs of the Studio Pre -- running those two (really shitty) analog cab sims in series seemed to kinda work, I'm guessing because it effectively steepened up the EQ cutoffs significantly. So yeah, the Studio Preamp will probably sound alright using it the way you propose.
I occasionally get a pang for that rig, but then look at prices and remember that I paid $119 for mine on ebay in 1997 when all of that stuff was going for super cheap since racks were uncool. I DID splurge on a Syn-2 and a few modules but . . . it was a pretty big splurge that I almost regretted when an unexpected $3k medical bill landed in the mailbox a couple months after I bought it...and I'm, not to be rude, pretty gainfully employed.
As a value proposition -- if you've got plugins that you think sound good, and you're going to be stuck playing at super low volumes or with headphones, AND you already have a Kraken preamp, AAAAANNNNNDDD you are currently unemployed...just chill for a bit. Maybe consider selling the FM3 if you don't love it and snagging a super cheap audio interface (I happily used a Behringer for many years alongside Fractal, etc. and don't consider the Universal Audio Solo I have now to be a huge sonic upgrade).