I use a Strymon BigSky reverb pedal in the effects loop of my HD500. Using similar types of reverb, I really can't tell the difference between the HD500 verb and the Strymon verb. The Strymon just has a few types of reverb that the HD500 doesn't and a cool hold function (although, the HD500 has a couple that the Strymon doesn't). The main reason I bought it was to reduce DSP usage on the HD500 (not 500X) for big patches and to get really over the top swells. That said, I can't imagine the Helix reverbs won't be as good or better than the HD500's, and I take it DSP won't be much of an issue.
I'll still probably use it with the Helix once I own one, if only because I look so cool carrying around a baby blue aluminum brick.
