I've actually done a side-by-side "shootout" with both of these speakers in the same room / system. While the N805s (orignal N805 speakers - not S, D, or Signature) are definately a more articulate (amd IMHO a better) speaker than the 12L, for the money the 12L is a good value. You'd really need to hear them side-by-side to judge if the increase in performance is worth the increase in cost.
Personally, if I were to take everything into consideration (looks, ability to hold the resale value, performance, etc.) I'd go with the 805's. If I was trying to save a buck, I'd go with the 12L's and never look back.