I made up the BSC with 2.2ohm 5W R and 0.82mh air choke. I tied the speakers with and without the BSC, with and without the grills and all combinations possible. The test music was a CD of heavy solo piano with massive dynamics and a thundering sound (analogue recorded):
http://musique.fnac.com/a2275526/Vladimir-Ashkenazy-Steinway-legends-digipack-CD-album.
End result BSC in and grills off. Though I felt as long as the BSC was in; grills on or off didn't seem as critical. Possibly the brighter mid-range was working against the grills here with BSC out. I felt also the BSC only effect the upper-mids and not lowers. This could be easily detected in the piano pieces as scales were worked from low to high. At this point BSC stays in and grills on.
This Ashkenazy\Steinway CD sounds its very best on the Oppo DBP-93\Paris\Fostex setup. On my main system with BDP-95\Silver Dragon 300BSE and large 3 way Osborns the dynamics are no where near as "startling" nor the sound as rich and natural (even raw).
On another note I jigged the Oppo BDP-93 to provide sub-woofer info during audio CD playback. It is always on with DVD play back as an LFE feed. But listening to the stereophile LF warble tones the speakers and set-up go down to 31hz before the bass really rolls-off. 40hz has a boost due to the port and has plenty of volume. The sub-woofer is not needed with this set-up and I re-jigged the Oppo not output bass to the sub-wooker during audio CD play back. In fact the Fostex boxes went lower than the sub-woofer with 12" bass driver in an 80L ported box!! After 31hz things go very quiet though.