Many people won't agree with me but here's my experience.
I got the Helix for 2 months, at first, I haven't been able to get a good sound with it and I was using stock cabs. Then I retried with Redwirez Ir's, sounded KILLER instantly.
Since that moment, I've been able to get the greatest tones I was looking for. After that I retried the stock cabs and definetly, I found them not as good as Redwirez Ir's.
But it's only my opinion and even if I haven't been able to make stock cabs sounds good, all the other stuff on the Helix is really great. Don't give up, it's a great unit.