My former MX119 is of similar generation as a MX135 as I remember. And I guarantee the MX 151 or 150 will reveal a new magnitude of sound in the Pure Stereo mode. The Dolby and DTS decoding is much superior to the 119. And the the ability of the 151 to up sample the video sources is startling.
I admit I had to wait FOR A PRISTINE 151 to come to Audio Classics. I can't see how you can go wrong investing in a pre-owned one. A 160 has neither the capability or the inputs to handle all video sources from component, S-video, video, as does a 151. Its a piece of work, and does the work very well. It has some quirks in programming, but we are all here to help if the need arises. I'm not saying a 119/135 are bad units, they most definitely are not. The 150/151 are just that much better.
The last time I heard a difference this large in between to Mac products is when I heard the difference between the much criticized C-24 phono section wipe a C-22 or when a MC 3500 at the same levels easily surpassed the sound capability of a 240 or 275.
I had come to believe over years the choice of amp had a bigger influence in a sound system. But in this instance the change in HT processor is really wondrous and to be enjoyed.
I'm watching Lincoln at the moment, and the quality of the rear channels is much superior and the detailing in off screen sources much more life like. Room noise, such as foot steps, air movement, room reverberation is much superior with the 151. The top octave is there, but doesn't stand out, it takes it proper place where with other HT processors the sound can be forced. The bass is firmer stronger and better defined with much better transients. The late night function works well and is not perceived a with the earlier units. Applause is more natural and authentic whether from an audience at a concert off mic or from folks on screen produced by the 3 front channels.