You have made a mistake by assuming 10's have " quicker response " as you call it. There's no such thing. It depends entirely on the manufacturer as to what any speaker reproduces and how it does that. You can get flabby 10's and tight 15's and so on.
Surely you will only be changing the cabs because of the tone you desire. Only 7 kg ( 3.5kg per cab ) is not worthing dumping your MB cabs for. Tone wise, if you prefer Bergs, then that is the best reason to change. If the Bergs were half the weight, i could understand , but they're not half the weight.
Stacking vertical is your best option for dispersion and getting the cabs nearer your ear. Adding extra cabs of identical nature , or removing indentical cabs, ususally affects the amount of air you can shift , rather then gaining or losing bottom end.