I think it's a rig issue. I've never been able to wrangle anything decent out of an HT5. The Madamp seems like a purpose-built early Fender clone. These things can be dark or spongy. If you look at the pickups you do like, they tend to be on the bright and aggro side, while the ones you don't are a little darker and thicker. There are some outliers, but that's my impression overall. What tones are you going after? Neither of those amps would be my first (or tenth...) for anything contemporary.