Are Sub-woofers really for music?

My system consists of an Audio Note Oto SE 10w and B&W CDM 1NT spealers. As i'vee posted in other threads my only nag is lack of low end. My speakers spec out out 60hz. The salesperson where i bought my speakers suggested I would NOT like a sub. and was not a good idea, Other than to impress my lower primate buddys. I listened to a pair of B&W 703s at the same store. While there was more bass present they lacked the mid details of my CDMs. The salesman said in order to get better lows and maintain my current sound Id have to step up quite a ways. I like this guy never did he try to "sell" me something he didnt think Id like.I also additioned a set of Audio Note AN-K/SP. These were nice but did not sound much better than the B&Ws in terms of the lows. In fact they may even have been a bit slower. I also suspect the efficiency rating was a bit optimistic.
So back to my initial question. Are there any "Music" subs? Can 1 sub actually do the job of two better speakers? If i turn the crossover down to "non-directional" low frequencys would this be too low below my 60hz rating and creat a hole? If I turned it up to crossover where my speakers drop off would it then be directional?
Speaker suggestions would be appriciated. Noting that I'm not going to replace my Oto. Im looking for the same sound I have now with a little more low end response. Maybe some ProAc's????