Looking at woofersetc.com the CL-S60 set has an upgraded tweeter (tw-24) from the standard CL-61A set (tw-19). It was my understanding that many people who were ordering this CL-S60 set were gettting the CL-61a with the tw-24 tweeter because Woofersetc.com were sold out of the s60 set. If this is the case and you get the CL-61a set with upgraded tweeter, you are making out.
I think the mid/woofer is the same on both sets, maybe just an older model or something. Pretty decent set for the money either way.