I realize this would degrade the sound somewhat and would definitely be a bad idea for fronts, but what about rears? "Soundstage" is not as important for the rears, so is there any harm in placing bookshelf speakers in a bookcase? The bookcases in question do not have a back, so the rear-ported speakers have a bit of space, about 6" from the wall. The Left speaker has a shelf all to its own, while the other speaker has books on either side of it (albeit novels, which come up to about the half way point of the speaker, leaving the top half free). BTW, the speakers are Mordaunt-Short 902, which have the rear port up high behind the tweeter, and are set to "Small," 100Hz crossover from my Marantz SR6200. They sound OK this way, but setting the speaker size to "Large" results in boomy bass, which I presume is a result of their closeness to the wall.