In my experience, if you take the xanax first and wait for it to kick in before you start drinking, you will have a hard time consuming enough alcohol to get to a dangerous level. Unless you are chugging hard liquor or playing drinking games, you will get dizzy and nauseous (and thus puke) long before the point of fatal toxicity. Puking gets rids of any unabsorbed alcohol in your stomach and usually diminishes your desire to drink more alcohol.
Irresponsible or not, I think that you would have to be dedicated to killing yourself to die from this combo. The worst thing that is likely to happen to you would be similar to the last time I took the combo. I took 2mg xanax and because I didn't get to this party until 2am and was sober, I started slaughtering beers off of the keg. I probably drank 9 or 10 Rolling Rocks between 2am and 5am. After that, the room felt like it was spinning and I went to bathroom and puked and almost fell asleep in there (I smoked someone else's dank earlier so that didn't help things). I managed to get up and go pass out on a couch. I don't remember most of the night, but I had an all day long hangover the next day (I never get hangovers from just alcohol anymore) and couldn't get off of the couch until that evening. I was just kind of half-awake/half-asleep most of the day. And still, some of my friends have done far worse, and lived to tell about it.
Another interesting thought is that there is some cross-tolerance between benzos and alcohol, so if you have a hefty alcohol tolerance, it will take more benzos than the average person to get sloshed. One of my alcoholic friend's once took 8mg xanax and drank about a case of beer (24 beers) over the course of a night. When I say he is an alcoholic, I mean it, so unless you have 3 dui's and a double digit number of other alcohol citations, don't take that much of either drug. He didn't even get sick though.
I will say that you should NOT drive a motor vehicle (including golf carts which I have seen people manage to drive into a house and get arrested for) when you combine benzos and alcohol in any amount. Too many people have destroyed their cars or hurt other people when trying to drive on this combo (of course they have no recollection of the event the next day).