You could also try the mod in front of the amp and see if you're getting the boost there, if putting the boost at the end of the chain in the loop doesn't work. I probably prefer delay and reverb in the loop if I'm using amp distortion (though some people like it in front), but modulation is about 50:50, you can make a case either way. It tends to sound a bit subtler up-front, so it depends on what you want.