I've been running my helix into the return of my 5150 III to date and have been "ok" with it. No unnecessary tones are added.
I went shopping on the weekend for a powercab...a knowledgeable salesman instead turned me to a Bose L1 Compact. I ended up renting the unit for the next month.
My first stab at it and the sound was amazingly good, well dispersed, no ear piercing noise if you stand directly in front of it, lots of volume. I'm jamming with it on Friday so I will see how it fits with the other superamps and drums but I have high hopes and dont regret it so far....even though I just rented.
Bose L1 Compact at Sweetwater