With the ICBM between the Denon and the Yamaha, it will affect SACD's and DVD-A's, but if you are using the digital output from the Denon for movies (which is what I usually recommend) then the ICBM would not do anything when watching movies. I'm not sure how the Denon 2910 does on bass management for DVD-A and SACD, so I don't know how much benefit the ICBM would provide - it could be either a subtle improvement (by allowing you to have some control over crossover points) if the 2910 does apply a standard 80Hz crossover, or it could be a significant improvement if the 2910 does no bass management. I would hope that a unit in the price range of the 2910 would offer at least basic bass management for both DVD-A and SACD, but I haven't gone through the manual to find out for certain.

You could use the ICBM with movies as well if you used the Denon's onboard Dolby Digital and DTS decoders (which could be done simply by selecting the six channel analog input on the Yamaha when playing a video DVD). I tend to stay with digital output for video DVD because my processor has always offered more processing capabilities (such as Pro Logic II, Dolby Digital EX, DTS ES) and bass management capabilities that negated the need for an ICBM, but that doesn't mean everyone should do the same thing I do.