I've done xanax and acid together, as well as valium and shrooms. I find I always have a better trip when I combine psychedelics with benzos. I don't particularly like psychs, because for me, there's always a lingering "uncomfortable" feeling, even if I'm having a good trip. How much experience do you have with each substance? If you haven't done shrooms much, I would recommend taking them by themself, and then to take the xanax if you start to get even slightly uncomfortable. If you're experienced and comfortable with shrooms, and just curious about the combo, go for it. I'd recommend not taking the xanax until you start tripping (i.e. don't take them at the same time), due to xanax's short duration. Have fun.