so there was the old mg line (mg dfx) and now there's the new line (mg fx)... what's different about the two?
Just a cosmetic difference I think.

They've just put a big MG label near where the knobs are.
The word is getting out about MG reliability and tone. So marshall says say its new and improved make a few cosmetic changes maybe change the name a little. Companies do it all the time. They do it with food but usually means the box is the same size with less food inside. So dont expect marshalls business model to change they are making a killing in profits on those amps so its doubtful they have done some soul searching and decided to actually make them better.