at JRRShop for $89.00...$75.65 with CODE: NEWSLETTER15

http://www.jrrshop.com/wa...ative-download-license

Bought it a week or two ago at Audio Deluxe.  I might have paid a little more for it but I still got a discount and I'm using it in projects already.
 
One thing to keep in mind is that although all the bands can be sidechained, the plugin can only receive one sidechain at a time.  So to duck my bass track at 68hz when the kick was present and simultaneously duck 250hz when the snare was present took two separate instances of C6.  I verified this with Waves support.  I thought a single instance would be able to receive 6 separate sidechains.

That would be a pretty cool feature, but I know of no multiband compressors that have more than one sidechain input.
 
Pro-MB probably has the most flexible sidechain implementation. You still only have one key input, but you can either assign it to individual bands or filter it separately.
 
For example, you could have sidechain frequencies from 100 Hz to 1000 Hz apply to band 1, sidechain frequencies from 4KHz to 8KHz apply to band 2, and have no sidechain input for band 3. In your scenario above, you could pull it off by routing both kick and snare to the multiband's sidechain input and then have 68Hz go to one band and 250Hz to another band.

Someone also turned me on to this product which looks really cool, as well.
 
 
http://www.youtube.com/watch?v=QR0NSr4vn6I