Oldguy's got it. Another cabinet will make a huge difference.

Also, raise the amp up to belly height or higher and angle it towards your head.

And finally tell the drummer to 'lay back on the brass.' Too much cymbal makes a mix sound like crap, washes everything else out on stage, folds back through the monitors and will eventually make you deaf. This I know. I also know that good drummers hit their drums but play their brass. Neil does not smash his cymbals. He hits them with just enough force to get the tone he wants from them. Tell your drummer to watch him and Mike Portnoy really closely. Not much force goes into the cymbals, it's finesse. This will clean up the mix and you might not even need another cabinet.