They are very close to SLO crunch channel (clean channel on crunch mode), which is indeed akin to JCM800 but still a bit different, less kerrang, bit more gain and ummmph.. Sounds good to me.
One of the best high gain 20 watt combo amps that I've ever owned! I just turn on an overdrive pedal and I'm wailing away. The Atomic 16 is also in that category minus the reverb. The price for the Atomic 16 is fair. I played an Atomic 16 combo amp at a local Guitar Center for about half an hour. I really liked that amp and knew that I would find one of my own one day.
I got mine when I traded a Lil' Dawg Champster 1x12 combo amp and a Marshall JCM 900 4501 combo amp. The previous owner thought the Astroverb 16 had too much gain and I offered him the 2 combo amps in trade which he went for. I removed the stock Eminence speaker and installed a Celestion G12M-25 speaker which made it sound much better since it's a high gain amp. I've also replaced the reverb tank recently as well and it's working fine now. I've seen the Astroverb amp as a 2x12 combo and an amp head. When Soldano was still running the company, you were able to order a custom amp head shell from them, but not any more.