Although the 7900 is a beast it only has a 1-2 db increase in SPL over the 7500/7700 amp. The cost is not in line with what I consider to be in line with the improvement .
Definitely the 7900 is a power headroom issue if cranked which in turn does not correlate evenly with the volume output. To really get the crank out one would need a huge subwoofer which will tear apart the room during an explosion scene.