I did hear the ELAC Atmos demo with $4200 worth of ELAC speakers and it was VERY impressive! It ultimately doesn't have the refinement, resolution, etc of a high end system but I'd love to have it for movies.
This is a valid statement. The Elac system, along with a $800 Marantz SR6011 would be a better system at $5,000 than most people will ever hear in their lives, for HT or movies. However, it is rare that we compare apples-to-apples. This system is the HT equivalent of a $1,500 two-channel system. I would say a typical two-channel rig for most AC members hovers around the $10-20K retail level. The HT equivalent might be closer to $25-50K.
Multichannel adds expense and complexity if we maintain equivalent quality to our two-channel rigs. This is aside from signal processing. Where a two-channel rig is mostly constrained to D/A conversion, equalization and bass management, multichannel is now applying processing to manage as many as 11 discrete channels plus LFE channels.