I think I get you but also think you mean I should split path 1a out to 1b after the effects I want before both amps? Having one 1a as effect into my first amp model and 1b just the effect, then I could take the output of 1b and route that to 2a. Otherwise I'd be feeding an amp output into another amps chain. Actually, this doesn't really work as in the patch I created, for cohesion, I fed the outputs of both heads into a single cab sim and reverb. I guess I could merge the amp heads on path 1 then have my cab and room sim on 2a being fed by path 1. I can only experiment I suppose.
Maybe it's not possible but I'd still sooner the dsp could handle more being thrown at it, per path, in it's current configuration. In all likelihood, I'd want to apply parallel processing to my vocal/synth chain too. I've previously built similar setups in DAWs on my 2010 macbook and could also play along with drum software utilizing hefty sample libraries. I'm just surprised that a dedicated, standalone effects processor (even if we're just talking per path) runs out of steam before a 6 year old computer running an operating system and it's myriad background tasks.
Also, back to the digital desk comparison. I'm familiar with many other desks but even at entry level.... I've installed a behringer x32 rack at a venue in my home town. Even it you're limiting it to processing it's physical inputs without hardware expansion, this unit processes 22 channels of incoming audio (including aux ins) with a gate, comp and fully parametric eq (including high and low pass). The same processing can be applied to all outputs. Again, if we're limiting it to the physical outputs it has, thats around 14 (including aux outs) I think. Besides all this you have a rack of 8 stereo or 16 mono effects, the sends to each can be processed with the afore-mentioned dynamics and eq, as can the returns. I'm sure it's possible but I'm yet to make it grey effects out due to lacking dsp. Oh, on top of all that, it animates input and output metering, rta on eq visualization and gain reduction on dynamics.
Granted, the modeling/processing in the x32 might differ greatly from that within the Helix... but that's a hell of a lot of processing that by comparison, what's considered an entry level digital desk is capable of.
Anyhow, I'm not hating on the helix, I'm just very surprised that my very first foray into patch creation, maxed it (that path) out. I think the routing is really clever and patch editing very intuitive and I'm sure I'll find a way to make it all work for me.