Just cuz he's 16, doesnt mean he's an idiot. You should still atleast tell the man that his goal of 2krms could cause some issues without electrical upgrades. Better to know from the begg. than to have to go fix it after ya eff something up.
As for the sub, if he's really interested in getting pretty loud, and wants to do something different than the average kid at his high school, he can try DC level 3s, AQ, or Sundown....or even better a custom built sub, then get the dustcap airbrushed or customized some way to fit him. Ish would be sick!
and please!!! tell him to go ahead and get good comps and amp them! dont be the typical high school kid with nothing but bass and nobody (not even the driver or passengers) knows what song they're listening to!!!