Although a radio anorak like most on here, I have to think that like Stephen , is increasing power on 648 going to be of any benefit now. Caroline is the only station I can receive now on Medium wave that plays regular music with a couple of much weaker Asian stations from London being the only others.
AM radio is all but dead now and increasing it's coverage will only make it reach a few more radio anoraks which are very small in numbers and will do nothing to increase the stations overall reach. In any case, the current AM signal already covers a huge area.
This is really off topic though as the thread is about analogue radio in general rather than a certain station and it's not before time that the few remaining stations should be able to use wider AM bandwidth if they want to even though as already stated, many receivers will simply cut off the extra bandwidth anyway so won't be heard.