If they really are going to end up on bookshelves, therefore very close to the rear wall, your options narrow down a bit, front porting or sealed-box design notwithstanding.
Take a look at North Creek Music's near-the-wall speakers. Along with the near-wall-specific design, George Short has built in world-class crossovers, innovative cabinet plans and IMHO terrific value. You can build them yourself as kits or get them made up.
Even if you don't go North Creek, the site contains a great deal of information pertinent to choosing any speaker which must go near the wall.
http://www.northcreekmusic.com/
Take a look at North Creek Music's near-the-wall speakers. Along with the near-wall-specific design, George Short has built in world-class crossovers, innovative cabinet plans and IMHO terrific value. You can build them yourself as kits or get them made up.
Even if you don't go North Creek, the site contains a great deal of information pertinent to choosing any speaker which must go near the wall.
http://www.northcreekmusic.com/