I've not tried that approach as I've tended to use EQ rather than filters, but I might give it a try this weekend. The filters in the Helix are very good so it will just be a matter of sketching out the signal path.
Assuming 1 input to Helix I'd probably split the signal straight away, then on 1 path into the filter and a compressor, and the other path for dirt. Then combine them. That would allow 1 big long chain with double DSP.
Or have the 1 input go to both paths entirely separately. 1 for filter / compressed low and the other for everything else. Then send them to the same outputs to combine or keep them apart for more FOH control, or 2 FRFR cabs etc.
What freqs would you set the filters at?