there is no way to turn off the cabs globally that i know of, but it wouldn't help anyway. you will have to pretty much start from scratch once you change the cab...because your preset will no longer be close to what it was (depending on which IR you load up).

I was worried you were going to say that... Ohh boy programming from scratch. Maybe some of your presets for an epsi combo pack thing?

the loop needs to be right after the amp model. i put the loop directly after the amp, but i have heard of others putting it at the very end of the chain to more closely simulate playing a full rack of effects through a guitar cabinet. i like having effects after the speakers because it's more "studio" sounding.