If good AA County public schools are your top concern, then I would stick with the Broadneck or Severna Park systems. With the budget cuts over the next several years, those systems will likely be the least impacted since they have such strong PTO/community support.
On the other hand, if you're happy where you are now, why move? It seems like an addition makes more sense, particularly if a good chunk of your mortgage is paid down.
Jeff
"Modern Society will find no solution to the ecological problem unless it takes a serious look at its lifestyles." -- Pope John Paul II