I don't know about your receiver Ken, but when I select the multichannel inputs on my Onkyo, it bypasses all signal processing, including speaker size and crossover, thus sending full range signals to all speakers.
My Denon 2910 has some bass management (speaker size, and distance), but it applies the same crossover point to all speakers. With the ICBM, I can select the appropriate crossover point for each speaker. If your HK applies it bass management to the multichannel inputs, then I don't think an ICBM would be an improvement.
