I was actually using the same HA3500 For my band duties for awhile and was in the same situation. , down tuned, gunshot loud drummer and guitarists through marshall stacks. I brought multiple class D amps to just our rehearsals and they couldn't cut it, I'm glad I didn't try it in show and be embarrassed. even if they had over the wattage rating of the hartke, I could run the hartke at 8 ohms and still have more clean power.So I've watched some reviews, read some threads, but I can't find a good answer on it so that's why I stared a new thread.
I am playing in a 2 hardcore bands - pretty low tunings. So I got a preamp and I had Hartke 3500 - a very nice tone, very nice build, but this head weights 15kg! The flight case on it made it even heavier. True - I could probably drive with a car over it and it will work and look perfectly, but this is everything but portable. So I decided to sell it and I did.
I came across the Trace Elliot Elf and I saw one guy using it - the fan was sounding like it is going to fly. Than I saw the Warwick Gnome series which took my interest.
I prefer to stick to the small size versions, so I am yet thinking about the standard Warwick Gnome 200w or the Pro v2 version 280w. I have Peavy 410cabinet 4ohm so I can take the max amount of the head in both situation.
Will the 200w be enough for rehearsal and gigs ?
My experience from this while portability is nice, there was an obvious sound quality and heft of bass missing that was there before.
I tried many different things. In the end it was obvious , the big iron brings the big balls.
I do have a gnome pro though and love it's features especially the pc recording interface. It sounds close to a gk rb. It could do the job on lower volume bands than what I was trying at the time. Speaker surface is the bigger importance overall.
Look for an GK RB. You will have alot lighter of an amp, not as deep and nicely portable. While having an awesome tone and reliability, and being quite a bit cheaper than most amps.