I already had a rack with one N72 that I bought assembled and I just finished building my first A12. It's 3 am so I can't do any extensive testing but everything seems perfect using a mic and headphones at all different volumes.
Update: Man, I can't believe how easy it was to build and how great it sounds. I thought there was a really loud phantom power pop, but it was just my monitoring at 3 am in headphones (it's still there but no worse than my N72).
I had a chance to test it out last night next to my N72 on my pair of 4047's on drums. Amazing. I actually consider it really clean and forward although I haven't driven it hard yet. And in comparison it really makes me appreciate the thickness of my N72. Now I just have to get the cash to buy a few more and another N72.
Thanks Tim, fast shipping and great product.