A simple calculation is in order: The MG1c's are 4 ohm speakers with an 85/db/watt sensitivity. Your Pioneer receiver is 100x5 channels into 8 ohms at 1% THD, so lets assume that into 4 ohms at clipping runs 160 watts or so, which translates into 16 watts RMS before the 10dB peaks typically present in musical material cause the amplifier to clip. 16 watts give a 12 dB increase in SPL, so a single channel into a single speaker will give a 97 dB average SPL at 1 meter. At 12 feet with both speakers playing, this translates into roughly 94 dB. You have to decide if this is enough. As far as HT use is concerned, the Magneplanars are bipolar: certainly the center channel is useful but since there is already a lot of reflected sound from the back of the MG's, the surround channels may just muddle the sound. Definitely get a self-powered subwoofer, the MG's need it!
