Interesting to read this review. I had a set myself - minus the sub - which I won from Lsound, before being pretty much forced to sell them
Still missing them... I only had the original MX5000 subs though, but at least I had a pair, and the integration and SQ in the setup was pretty excellent. I fully plan to own another set...
To answer some questions:
The Q125s have a fairly insane 300W RMS power handling, and are 4-ohm nominal impedance speakers.
They are rated down to 60Hz at -3dBs if I recall correctly. As that's the frequency subs start to sound localisable you might like to experiment with crossing over the sub at 60Hz and not 80Hz?
The little rubber feet aren't entirely useless, they worked for me!
Lack of 12v trigger IS an issue and you're right to raise it - KK Sound should take the consumer market more seriously. The more feedback they get - directly and via forum discussion - the better the chance they'll get the hint. A 12V trigger input wouldn't hurt sound quality, it might add a bit to the BOM and base cost, but who's gonna complain? We want it - give it to us.
You can't buy a separate Q125 as a centre because - as you know, actually - they're packed and shipped as pairs. It was the same deal with LS50s... You'll need to find someone else buying a Quattro setup and split a pair with them. That said, the centre is only different because of the mount (which worked for me, I found it useful) and iirc the rear panel is rotated 90 degrees. You don't have to use the mount, either.
I'm intrigued by your positioning of the TriFXs - I went with side mounting, albeit too high up (unavoidable in my room) to get a better sense of audio panning and surround... I never liked rear-mounted speakers in a 5.1 system! Did you experiment with positioning? I am pretty sure they're meant to be wall mounted, hence the lack of stands.
Speaking of stands, what do you think of the Q125 stands? I thought they were expensive at ÂŁ600/pair but at least they match, visually... How heavy are they, really? And how stable?
Any temptation to add more subs?
Lastly, I know you have small hands!
Very jealous actually, I miss having any kind of audio system right now, and the Quattro package in particular!