400 vs 440 Pro

[Spindrift]

I've got my 440 Pro up and running, and, although it's early days, I thought I'd post my findings so far.
Whereas I used to listen at fairly low volume at -25dB, now I have to turn it down to about -30 to get the same volume level. Not sure whether things have been recalibrated or it's the extra 40W coming into play.
Sitting here listening and reading at the same time, I keep being distracted by things like a hard panned vocal disappearing far left and keeping on going. The soundstage is huge! Depth improvement is also audible. Reverberation trails going on seemingly forever. Bass notes going lower than I can remember them on the 400.
I wasn't expecting much until the amps. had 50 or so hours on them, but clearly the 440 is a major step up in performance. The treble is clear and smooth, without a hint of glare, grain or hardness. Not that the 400 was harsh in the treble department, but the 440 sounds smoother to my ears.
The 400 could sometimes sound a bit "thin" but the 440 seems fuller somehow. Please excuse my descriptions of my findings, I'm no professional reviewer by any means! Running temperatures are lower; one of my amps is wall mounted, the other in a rack with isolation pucks underneath which raise the amp. 40 mm off the deck and give improved airflow. Temperatures on the wall mounted unit: A 33 D 36 and PS 41, with those on the rack mounted unit being a couple of degrees above this. Even listening at lower volume on the 400, the temps. used to be in the mid to high 40s on both amps, the one on the rack always running a few degrees hotter than the wall mounter. I've also made some cable changes, swapping out a cable with adapters for a beautifully made Cabledyne RCA to AES/EBU 110 Ohm Master to Companion connection and also the new Audioquest mains cables, all of which will need to be burnt in
I only had a chance to listen for a couple of hours, but I'll give it another whack tomorrow and report any other changes I've noticed. 
Oh, and when you switch the amps. off, they go stone cold which is good for your electricity bill, but might mean that they'll will take longer to warm up and come on song.
Looking forward to other 440 ownwers reporting their findings.

Thanks for that great review - I am on the tipping point of ordering the 440 and really appreciated the perspective - sounds like I'll need to pull the trigger . . ! (Especially your comments re treble and sense of thinness vs fuller sound)