Hi
Don't know if this helps you, but I made a cheat sheet to have at hand - https://www.dropbox.com/s/w6pvbv1l0t0b5cf/Line6 Helix-Model Summary%2C 2%2C60-P1.0-01.pdf?dl=0. If you like quick info it's handy. If you like it in on-line format there is some sites online. I included this one - http://www.helixhelp.com/, with great info and very useful.
I also included another address in the document (could not include it in the post by some reason...) to a forum post with massive info about all models. One on the info sources I used for my document above. I actually think this is the original info that is used on the helixhelp-site. Anyway, really a great job on both places.
Enjoy. //Per