Quick initials impressions after 30 minutes.
1. The Vali sounds better than the magni (bear in mind that I didn't care much for the magni...I thought it was somewhat bright/harsh without much punch...also I used magni with modi and now I have uberfrost)
2. I experienced the same ringing for the first couple of minutes that others have commented on. After that I have not had any microphonics at all even when tapping the top of the case, plugging or unplugging hp's or changing out the RCA's. (note that I'm using blutack on the corners to mount to my heavy desk...I have not finished the isolation block yet but should be done with it in the next day or so). So far the only time I get any extra noise is when I turn the amp off and then back on.
3. The Vali seems to have the ability to reach a "loud" listening level very quickly. The lyr and A2 both have more play on the pot. They both allow me more play on the volume pot without seeming "loud" as the sound seem to just fill in and not blare. Hope that makes sense.
4. The hd650 sounds better so far than the he500 on the Vali. The he500 seems a little treble happy now. This may change with burn in. I can hear sibilants that I've not heard with the he500 before. Haven't tried any other hp's yet.
5. Build quality seems decent for the price. The amp has a good weight to it.
6. Just tried the ma900 with the Vali. NOT a good match IMO because of the noise that can be quite audible even during playback. I'm disappointed that the Vali does not pair well with this hp. Might be a deal breaker for me.
Okay, back to listening and burn in.