Ok - Calibrated the AV gear, test track was a Pink song, 2ch - Played as 2CH (Yami set to Straight), 5.1 JRSS (Yami set to Straight), and for comparison the 5.1 Up Mix done by the Yami as measured/observed from one seating position.
Measured Differences:
a) 5.1Yami is 3db louder than 2ch
b) 5.1JRSS is 4.5db louder than 2ch (or 1.5db louder than the 5.1Yami)
c) Centre Channel Only (rest muted) 5.1JRSS center CH is 0.5db louder than the 5.1Yami
Observed Differences: I think the JRSS 5.1 upmix sounds good. The 5.1JRSS centre ch does sound more "pronounced" than the 5.1Yami but to my ears this is not a bad thing as it still gives some central focused localisation to the sound stage. That said the overall increase in loudness always produces a positive impression in A/B tests, and 5.1JRSS is the loudest (= sounds best??). With 5.1 upmixing there is no "one right way" just preferences. I'd suggest you add two things to suit all tastes (especially as according to the other post you are looking at adding more "pre-amp" style features to MC):
1) Adjustable Sound Level per channel
2) Pink Noise playback per channel so you can balance the output
Result: This was a good test for me as I like to listen to music Upmixed to 5.1 unless I'm sitting in the 2ch sweet spot (and I'm not much of a sit and listen type). My initi8al impression was that I liked the 5.1JRSS colouration better that 5.1Yami's for Upmixing. I also like that with JRSS it will only apply to my Music and leave the Direct Show playback untouched. The result is potentially less switching of sound modes on the Yami to suit the source played via MC, eg I like:
a) DTV (2.0 or 5.1) = Yami's DSP-Movie settings as it places dialogue out of the Centre Channel even on 2CH sources
b) Music (2.0) = Normally 5.1 mix so I would use Yami's DSP-5.1CH Mix, when I wanted to listen as 2.0 I'd turn off Yami's DSP to Straight
c) Movies (mostly 5.1, some 2.0 music videos etc) = Either leave Yami's DSP-Movie or turn it to Straight for 5.1, and use Yami's DSP-5.1 mix for 2.0 Music Video
If I now turn on 5.1-JRSS in MC I can leave the Yami on Movie most of the time (it will process the JRSS again but....I'll have to see how it al sounds over a period).
Thanks
Nathan