I use D'Addario 10-52 gauge strings on my guitars, and they have a nice and beefy tone to them. If the strings aren't able to fit in the nut slot they will need to be filed a bit by someone who knows what they're doing. Using a string that is too big for the slot can potentially break the nut, and will most likely cause some minor tuning issues. In other words, if it won't go easily, don't make it. Moving to heavier strings also means that your guitar's intonation will need to be set, and the truss rod might need to be adjusted. These are all relatively simple adjustments, but it's best to let someone who knows what they're doing handle the job.

ps. Welcome to GT!