OK, here we are... after 1 day of break-in my
very first conclusion is that the SP1000 Amp really improves on the SP1000 when driving the VC.
Sound level wise, with my Verite Closed on the SP1000 alone I have to set-up volume at 120 (/ 150) while with the Amp, the volume (with high gain) is set at 100 (/ 150) and at 110 (/150) with low gain.
This may seems not to be a major improvement, but the interesting part is elsewhere: With the Amp, the dynamic and spacious sound is back...close to what I get from the VC with my Desktop EC445 amp. Without the SP1000 amp, the VC sound is "flat" and boring. And the difference is not subtil...
I also noticed that "low gain" set-up of the Amp is even more pleasant than "High gain" which may be sometime agressive (but... with the VC "high gain" may be needed depending on the recording and your listening ). I recommand you try booth and do not directly jump to High-gain.
Now I will try with IEMs and Shure KSE1500 but to see if they also benefit from the added space and musicality of the Amp, even if they do not need the added output power. Tests will tell... but I think that with those IEMs I will always use the "low gain" set-up of the Amp.