I've loaded 8 amps into my DT50 through the DT50 Customizer. I find if I run straight into the amp, I get a little more gain than if I ran the HD400 into DT50 with the EXACT model PREAMP (not full) settings? The basic tone is still there, it's just the gain issue. I use the Plexi Bright model and I'm using a Strat with low output pickups so I need all the gain I can get!!
I'd prefer to use the HD400 via L6 if I can get this sorted because for now I find I like the tones of the amp with my own pedals out front (BB Preamp) and in the loop (I can't find a delay I like as much as my TC Electronic Flashback) I gotta say I don't like the volume increase when the modulation and delay effects are engaged too?
Otherwise the rig is INSANELY awesome and is one of the best rigs Ive owned and I have had many, many fine valve amps so kudus to Line 6 from producing this fine piece of gear.
I just love it!!