I've owned both at the same time, and it's like comparing apples and oranges. You see I have this split personality disorder where on one hand I listen to room sized speakers using 5 watt single ended toob amps, and OTOH, I listen to much smaller speakers using amps you can weld with. Anyway, I'm not sure I can easily explain the differences between the current hog Infinitys and the electon sipping Altecs. I also have a pair of Infinity RSIIbs, which to my ear sound better than the K-9s. There is something quite pleasing about EMIMs and EMITs in a nice dipole configuration and enough room to allow them too breathe.

Bottom line though I traded the K-9s not too long ago for a VPI TT, because I found the K-9s bass heavy and muddy compared to the RSIIbs. Now when I'm watching movies, I have the Altecs and the Infinitys all running from the same source, and the sound is quite good...