There are exceptions to the empty stomach. One would be Opana (which, in the pursuit of getting high) shouldn't be taken on an empty stomach, but rather after a meal with a high fat content. It actually has the same increase in effect if taken intranasally or IV.
With amphetamines you want to have a more neutral stomach pH, as a previous poster mentioned. This can be accomplished by taking baking soda (yuk) or Tums about half an hour before taking them. This only works with the oral ROA.
I've found that Soma works best taken around a light meal, such as soup, a small sandwich, some fruit, crackers, or anything like that (not all those together).