I can't speak for the overtone specifically but i owned a ceriatone 1987x for about 3 years before i sold it to pay for some stuff. It was a really great amp. Would have probably gotten a ceriatone 18 watt if i didn't find such a good deal on another 18watt around here
Can't compare the actual product, but Ceriatone has been solid, ships amps on time, and has well-regarded customer service. If you order Ceriatone, you can be pretty assured you'll see your amp, and in reasonable time, at least within the lead time quoted. And f you want the OTS modded for anything specific, they are all custom built to taste.
In turn, some other companies has gone through periods were people weren't getting their order or any communication and many have thought the company was out of business more than once. And while they may build a great product, they are known for falling way behind quoted lead times and for poor and unresponsive customer service. I think they are just always overwhelmed. If you buy something from one of these companies, save some headache and $$$ and buy used, they pop up relatively often on TGP or eBay.
It would be a no-brainer if it were my cash. If I were going D*mble and wanted a more developed, more featured, higher priced amp that Ceriatone, I would buy a Fuchs, even if I had to go used, but honestly, I would probably stick to Ceriatone.
I dealt with the now-defunct amp company on getting a vintage cabinet restored (he built clones of, and restored, vintage Gibson circuits). He would screen phone calls and email maybe every 6 months with a new excuse. It took a threat of legal action to get my cabinet back, which hadn't been touched in the nearly TWO years he had it. And I was still $300 out of pocket that I just wrote off as a deal gone bad. Now, I would never jump into a deal with a company known for late delivery and poor communication, a total lack of professionalism.