Id use a send block to the BJ and any old amplifier for the sound coming from the helix sims.
My story goes like this.
A few years ago i bought an old valve carlsbro pa 60 which i dicked around with replacing caps and such. I cascaded 3 of the input valve channels to get some drive but wasn't impressed. I had planned to clone a 2204 preamp and rip out the pa 60 pre's all together. Since at the time i had a 1992 (basically a plexi)
I lost interest.
Couple of months ago i bought a jet city 20w head which by the way is awesome i retired the superbass as it has one sound. It sounded awesome, but sometimes you want something different y'know.
Few weeks ago i got my helix floor and the plan was the 4cm. After a while messing around with ground loop issues the thought occurred to me to use the carlsbro as a valve power amp.
I've been using only preamp models from the helix and its better than anything ive played through.
Full disclosure tho. I do have an early 70's 4x12 with 25watt pulsonic cones soooooo.
But yeah i fully endorse going into an effects return and utilizing helix's potential.