I've used the 500x a lot in the last few weeks and have got everything tweaked how I like on my main patches.
I'm using the SVT, B-15 and GK amps sims and I have to say I'm mightily impressed. This is now my goto rig either with or without back line.
I'm not going to bother with the helix for now as the 500x is doing all I need.
Still haven't tried the 4 cable method yet, soon maybe.