The CM6, like most of the B&W aluminum tweeters, tend to sound a bit brighter than soft fabric domes. If the bass response of the speaker is limited (the CM6 is -6dB @ 45Hz, not sure what the -3dB frequency would be, 60Hz?), the overall presentation can sound somewhat thin and bright.
The ASW 650 subwoofer should be able to add a decent amount of bass (but maybe not the highest quality bass) with a 12" driver and 200W RMS, but I don't know the size of your room your trying to fill, the layout or the bass management settings. Is the Oppo 105D functioning as preamp and bass management? Are the mains being high-pass filtered? What is the low-pass setting of the subwoofer?
Location has a lot to do with it, and without measuring equipment many users move about the room and find the location where the bass output is lowest, then try placing the subwoofer at that location. Lots of variables here, fill in the rest of the needed information for us.
When you upgrade to the larger B&Ws things will change, but you may want to upgrade the subwoofer to match quality. If you have a big budget the JL Audio subs are hard to beat. The Rythmik servo subwoofers are a good value, and having a pair (or three) to even out room response can often go a long way in bettering a single big bad expensive subwoofer.
Steve
