The B&W 685 S2 is a small bookshelf speaker with a single 6.5" woofer. B&W specifies them 53 Hz, but that is an anechoic measurement, and your in-room measurements could be completely different.
Audyssey measures the in-room response of the speakers and sets the crossovers accordingly. Audyssey will not provide any correction below the crossover frequency it set. (Correction could only involve "boost" below the low frequency roll-off point, and Audyssey won't boost below that because it could endanger the speaker.) Therefore, if Audyssey set the crossovers to 120 Hz, and you *lower* the crossovers after running Audyssey, there will be NO CORRECTION applied below 120 Hz. If Audyssey set the crossovers to 120 Hz, DO NOT lower the crossovers to 80 Hz. Not only could you endanger your speakers, (slightly), but you'll have a "hole" in the room correction between 80 and 120 Hz.
The only possible issues to consider with a 120 Hz crossover are the potential for sub localization, and the possibility that your sub is not capable of flat response to 120 Hz. If you're not hearing sounds coming directly from your subs, like male voices, or other low mid-range sounds, sub localization is not a problem. According to Hsu, that sub is flat to 200 Hz, so the second issue is not a problem:
To your question at hand, (system not sounding "crisp"), this could be many things. The first thing we need is a better definition of what your expectations are. Are you missing the high frequencies? Is dialogue muffled and hard to understand? Is the bass overwhelming? Does it sound like the room is too "echo-y"?
Is the lack of crispness on all sources, or just one or some? How do you have your sources, (BluRay/DVD/CATV/Streaming) connected to your receiver? Is everything set to Bitstream? Make sure everything is connected via HDMI and set to output Bistream.
Audyssey Dynamic EQ should not affect "crispness" per se'
but it does make the bass more prominent at lower listening levels. Try using a 5 or 10 dB Reference Level Offset, which will decrease the amount of bass prominence by changing the point where Dynamic EQ is added to the signal.
Room treatments can also help, as mentioned above. However, until we have a better understanding of the exact problem and what's causing it, it's hard to be more specific. I presume you don't have any kind of measurement gear to measure your acoustics or your system?